CN106786713B

CN106786713B - A kind of voltage source converter unit topological structure and control method

Info

Publication number: CN106786713B
Application number: CN201611059115.3A
Authority: CN
Inventors: 鲁江; 卢宇; 董云龙; 汪楠楠; 王永平; 赵文强; 田杰; 李海英
Original assignee: NR Electric Co Ltd; NR Engineering Co Ltd
Current assignee: NR Electric Co Ltd; NR Engineering Co Ltd
Priority date: 2016-11-25
Filing date: 2016-11-25
Publication date: 2019-04-09
Anticipated expiration: 2036-11-25
Also published as: CN106786713A

Abstract

The invention discloses a kind of voltage source converter unit topological structures, it include: the first unit isolation switch (D1) being serially connected, cell isolation switch (S1), voltage source converter, second unit isolation switch (D2) and connecting wire, the first direct current endpoint (X1) and the second direct current endpoint (X2) of the beginning and end of the series loop respectively as the voltage source converter unit；Unit bypass disconnecting link (D3) is connected across between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Unit bypass switchs (S2), is connected across between the nearly voltage source converter end (Y1) of first unit isolation switch (D1) and the nearly voltage source converter end (Y2) of second unit isolation switch (D2).The invention also discloses the corresponding control methods of the topological structure.The present invention when realizing two or more inverter series operations of DC transmission system single voltage source converter online put into and exit.

Description

A kind of voltage source converter unit topological structure and control method

Technical field

The invention belongs to technical field of direct current power transmission, and in particular to a kind of voltage source converter unit topological structure and control Method.

Background technique

HVDC transmission system can be divided into two types: the customary DC transmission system based on thyristor transverter (LCC-HVDC) and the flexible HVDC transmission system based on full-control type voltage source converter (VSC-HVDC).Customary DC transmission of electricity system Uniting, at low cost, loss is small, running technology is mature, and the DC transmission system overwhelming majority being currently running in the world at present is all LCC- HVDC system, but customary DC transmission system there are inverter side easily occur commutation failure, it is strong to the dependence of AC system, need to inhale Receive a large amount of reactive powers, the disadvantages of converter station takes up a large area；And then have can be real for the flexible HVDC transmission system of a new generation Existing active power and reactive power decoupling control, can power to passive network, compact-sized occupied area is small, commutation is not present The advantages that failure problem, but there is also the defects of higher cost.Therefore, both comprehensive customary DC transmission of electricity and flexible DC transmission Advantage, one end converter station use the Hybrid HVDC skill of voltage source converter using thyristor transverter, other end converter station Art has good future in engineering applications.From the point of view of long term, with the reduction of full-controlled device price used in voltage source converter, both ends The flexible DC transmission technology that converter station is all made of voltage source converter will also have been more and more widely used.

In order to meet the transmission of electricity demand of remote large capacity, customary DC power transmission engineering is changed using two or more thyristors The concatenated technology of device is flowed to promote the DC voltage level and transmission capacity of DC transmission system, and the current country has multiple brilliant locks Pipe inverter tandem type DC transmission engineering, which is built up, to put into operation.For one end converter station using thyristor transverter series connection, the other end Converter station is all made of voltage source converter using the concatenated tandem type Hybrid HVDC technology of voltage source converter and both ends Concatenated tandem type flexible DC transmission technology is still in conceptual phase at present.

Common bipolar direct current transmission system is made of positive and negative two direct current pole, as shown in figure 3, each direct current pole is packet The converter valve of station containing sending end, a complete direct current transportation circuit by end station converter valve, DC power transmission line and earthing pole.

Requirement for the DC transmission system using inverter serial connection technology, to major loop topological structure and control system Be that by the online investment of inverter in the operational process of direct current pole and exit online, with meet direct current pole two or two with Following demand when upper inverter series operation: 1) single inverter can be exited normally manually is overhauled, after maintenance It can put into and continue to run；2) it can be exited when single inverter breaks down with automatic fault；3) the online throwing of single inverter Move back the normal operation for not influencing other inverters, the demand can guarantee the operation of tandem type DC transmission system flexibility and Reliability.The topological structure of thyristor transverter tandem type DC transmission system and the throwing annealing method of thyristor transverter are equal at present It is mature.

For tandem type Hybrid HVDC system and tandem type flexible HVDC transmission system, such as still changed using thyristor The online throwing that the topological structure of stream device tandem type DC transmission system carries out voltage source converter is moved back, since voltage source converter is deposited In capacitive energy storage element, voltage source converter can be caused the catastrophe failure of similar DC side anode, cathode short circuit occur, cause to change Stream device throwing, which is moved back, unsuccessfully to be had not yet to see voltage source converter in achievable tandem type DC transmission system and throws the topology moved back online Structure and control method are suggested, it is therefore necessary to provide a kind of achievable voltage source converter in conjunction with the characteristics of voltage source converter Device throws the topological structure moved back and control method online, defeated to meet tandem type Hybrid HVDC system or tandem type flexible direct current The operation and maintenance of electric system need.

Summary of the invention

It is an object of the invention in view of the shortcomings of the prior art, providing a kind of voltage source converter unit topology merging Method, single voltage source when for realizing two or more voltage source converter series operations of DC transmission system DC pole The online of inverter puts into and exits online, can satisfy tandem type Hybrid HVDC system or tandem type flexible DC transmission The operation and maintenance of system need.

In order to achieve the above objectives, the technical solution adopted by the present invention is that: a kind of voltage source converter unit topology is provided Structure, it is characterised in that: switch (S1), voltage source including the first unit isolation switch (D1) by being serially connected, cell isolation The series loop that inverter, second unit isolation switch (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop Respectively as the first direct current endpoint (X1) and the second direct current endpoint (X2) of the voltage source converter unit, it is used for and other voltages Source inverter unit is connected；

Further include unit bypass disconnecting link (D3), is connected across the first direct current endpoint (X1) and the second direct current endpoint (X2) Between；

Further include unit bypass switch (S2), is connected across the nearly voltage source converter of the first unit isolation switch (D1) Between device end (Y1) and the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

Topological structure i) the first direct current endpoint (X1) is successively through first unit isolation switch (D1), cell isolation switch (S1) It is connected to voltage source converter anode (Z1), the second direct current endpoint (X2) is connected to voltage source through second unit isolation switch (D2) Inverter negative terminal (Z2)；

Topological structure ii) the first direct current endpoint (X1) through first unit isolation switch (D1) is being connected to voltage source converter just It holds (Z1), the second direct current endpoint (X2) is successively connected to voltage through second unit isolation switch (D2), cell isolation switch (S1) Source inverter negative terminal (Z2).

In above scheme, voltage source converter in voltage source converter unit using modular multilevel structure and including The submodule of following two types or one of type:

First kind submodule is the submodule that positive and negative zero three classes level can be exported under non-blocked state；

Second class submodule be can only be exported under non-blocked state just, the submodule of zero liang of class level.

In above scheme, under the submodule configuration mode of the bridge arm of voltage source converter includes in voltage source converter unit State two kinds:

Mode one, every mutually upper and lower bridge arm are made of the first kind sub-module cascade；

Mode two, every mutually upper and lower bridge arm are by the first kind submodule, the second class submodule two types submodule The mixing bridge arm of composition is cascaded, the quantity configuration ratio of each two seed module of bridge arm is identical, and in two types submodule capacitor In the identical situation of voltage rating, the quantity configuration ratio of first kind submodule is more than or equal to 50% in each bridge arm.

Configurable current-limiting resistance is thrown online for inverter unit in above scheme, in voltage source converter unit moves back process In flow through voltage source converter DC current limitation control, it is characterised in that: topological structure further includes current-limiting resistance (R1) With resistance by-pass switch (S3), resistance by-pass switch (S3) is in parallel with current-limiting resistance (R1), and then is connected on the topology In structure i), the nearly voltage source converter end (Y2) of voltage source converter negative terminal (Z2) and second unit isolation switch (D2) it Between connect；Alternatively, resistance by-pass switch (S3) is in parallel with current-limiting resistance (R1), and then it is connected on the structure ii) in, It connects between voltage source converter anode (Z1) and the nearly voltage source converter end (Y1) of first unit isolation switch (D1).

In above scheme, it can configure in voltage source converter unit and exit processing unit for realizing voltage source converter list Member exiting in the operational process of direct current pole online, it is characterised in that: further include being formed by least one semiconductor switch device Exit processing unit；It is described to exit processing unit and be connected between the anode of voltage source converter and negative terminal or in parallel It connects between the anode and negative terminal of voltage source converter submodule；The semiconductor switch device conducting side for exiting processing unit To consistent with the DC current direction of voltage source converter is flowed through, and remain and cut in voltage source converter normal course of operation Only state.

In above scheme, the semiconductor switch device for exiting processing unit is half control type switching device, or full control Type switching device.

In above scheme, the semiconductor switch device for exiting processing unit is single semiconductor switch device, or It is multiple semiconductor switch device series connection and/or parallel connection.

In above scheme, the processing unit that exits further includes at least one inductance, the inductance and semiconductor switching device Part is connected in series.

In above scheme, the inductance for exiting processing unit be single inductance or multiple inductance series connection and/or simultaneously Connection.

In addition, the present invention also provides a kind of control method of voltage source converter unit topological structure, the voltage source is changed Stream device unit topological structure includes first unit isolation switch (D1), cell isolation switch (S1), voltage source by being serially connected The series loop that inverter, second unit isolation switch (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop Respectively as the first direct current endpoint (X1) and the second direct current endpoint (X2) of the voltage source converter unit, it is used for and other voltages Source inverter unit is connected；Further include unit bypass disconnecting link (D3), is connected across the first direct current endpoint (X1) and Between two direct current endpoints (X2)；Further include unit bypass switch (S2), is connected across the first unit isolation switch (D1) Between nearly voltage source converter end (Y1) and the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

Topological structure ii) the first direct current endpoint (X1) through first unit isolation switch (D1) is being connected to voltage source converter just It holds (Z1), the second direct current endpoint (X2) is successively connected to voltage through second unit isolation switch (D2), cell isolation switch (S1) Source inverter negative terminal (Z2)；

It is characterized by: realize online investment of the voltage source converter unit in the operational process of direct current pole, and include with Lower step:

Step 1: receive issue voltage source converter unit investment order, treat investment voltage source converter unit into Row attended operation sequentially closes second unit isolation switch (D2), closes first unit isolation switch (D1), closes unit bypass Switch (S2) pulls open unit bypass disconnecting link (D3)；

Step 2: it closes the change of current corresponding to voltage source converter unit to be put into and becomes incoming switch and treat investment voltage Voltage source converter in the inverter unit of source carries out charge control, and the voltage source in voltage source converter unit to be put into is changed The capacitance voltage of stream each bridge arm submodule of device is charged to close to rated value；

Step 3: unlocking the voltage source converter in voltage source converter unit to be put into and controls the direct current of its output Press (U_d) it is 0；

Step 4: closing the cell isolation switch (S1) in voltage source converter unit to be put into, and control is flowed through wait put into DC current (the I of voltage source converter in voltage source converter unit_d) to DC current with working voltage source inverter The unit bypass switch (S2) in voltage source converter unit to be put into is pulled open when actual measured value is of substantially equal；

Step 5: converter station where voltage source converter unit such as to be put into is DC voltage control station, then controls wait throw Enter the DC voltage (U that voltage source converter exports in voltage source converter unit_d) to operational objective value；Voltage source such as to be put into Converter station where inverter unit is DC current control station or dc power control station, then control flows through voltage source to be put into and changes Flow the DC current (I of voltage source converter in device unit_d) to operational objective value；Later, voltage source converter unit to be put into Investment is completed.

It puts into step 3, controls electric in voltage source converter unit to be put into online in above-mentioned voltage source converter unit DC voltage (the U of Source Con-verters output_d) be 0 control method, specifically include: will be in each bridge arm of the voltage source converter First kind submodule normal release simultaneously exports the Voltage Reference wave to match with alternating voltage, the electricity of every mutually upper and lower bridge arm output And opposite in phase equal with reference to wave amplitude is pressed, if being configured with the second class submodule, the second class in voltage source converter bridge arm Submodule is bypassed and is exited.

Wherein, the first kind submodule is the submodule that positive and negative zero three classes level can be exported under non-blocked state, The second class submodule be can only be exported under non-blocked state just, the submodule of zero liang of class level.

During above-mentioned voltage source converter unit is put into online, according to first investment DC current control station or direct current function The voltage source converter unit of rate control station, the sequence progress for the voltage source converter unit for putting into DC voltage control station again are electric The online investment of Source Con-verters unit operates.

The present invention also provides a kind of control method of voltage source converter unit topological structure, the voltage source converter list First topological structure include by be serially connected first unit isolation switch (D1), cell isolation switch (S1), voltage source converter, The series loop that second unit isolation switch (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop respectively as The the first direct current endpoint (X1) and the second direct current endpoint (X2) of the voltage source converter unit are used for and other voltage source converters Unit is connected；Further include unit bypass disconnecting link (D3), is connected across the first direct current endpoint (X1) and the second DC terminal Between point (X2)；Further include unit bypass switch (S2), is connected across the nearly voltage source of the first unit isolation switch (D1) Between inverter end (Y1) and the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

It is characterized by: realizing that online in the operational process of direct current pole of voltage source converter unit normally exits, and wrap Containing following steps:

Step 1: it receives the voltage source converter unit issued and exits command, control voltage source converter unit to be retired DC voltage (the U of middle voltage source converter output_d) drop to 0；

Step 2: the unit bypass switch (S2) in voltage source converter unit to be retired is closed, electricity to be retired is flowed through The DC current of voltage source converter is transferred to unit bypass switch (S2) in Source Con-verters unit；

Step 3: it pulls open the cell isolation switch (S1) in voltage source converter unit to be retired and is latched voltage to be retired Voltage source converter in the inverter unit of source；

Step 4: isolated operation is carried out to voltage source converter unit to be retired, sequentially pulls open voltage source converter to be retired The change of current corresponding to device unit becomes incoming switch, closes unit bypass disconnecting link (D3), pull open unit bypass switch (S2), pull open the One cell isolation disconnecting link (D1) pulls open second unit isolation switch (D2), and voltage source converter unit to be retired exits completion.

In above-mentioned voltage source converter online normal exit step one, control electric in voltage source converter unit to be retired DC voltage (the U of Source Con-verters output_d) method that drops to 0, it specifically includes: will be in each bridge arm of the voltage source converter First kind submodule keeps normal release and exports the Voltage Reference wave to match with alternating voltage, every mutually upper and lower bridge arm output Voltage Reference wave amplitude is equal and opposite in phase, as being configured with the second class submodule in voltage source converter bridge arm, then second Class submodule is bypassed and is exited.

During above-mentioned voltage source converter unit normally exits online, according to the electricity for first exiting DC voltage control station Source Con-verters unit, exit again DC current control station or dc power control station voltage source converter unit sequence into The online of row voltage source converter unit normally exits operation.

Further, the voltage source converter unit topological structure further includes by least one semiconductor switch device shape At exit processing unit；It is described to exit processing unit and be connected between the anode of voltage source converter and negative terminal, or simultaneously It is connected between the anode and negative terminal of voltage source converter submodule；The semiconductor switch device conducting for exiting processing unit Direction is consistent with the DC current direction of voltage source converter is flowed through, and remains in voltage source converter normal course of operation End shape；Process normally is exited for being configured with the online of voltage source converter unit for exiting processing unit, above-mentioned It further include step A between step 1 and step 2: by exiting all half in processing unit for voltage source converter unit to be retired Conductor switching device triggering and conducting is DC current (I_d) current channel is provided；Further include between step 3 and step 4 Step B: be latched voltage source converter unit to be retired exits all semiconductor switch devices in processing unit.

The series loop includes following two kinds of topological structures:

The voltage source converter unit topological structure further includes being exited by what at least one semiconductor switch device was formed Processing unit；It is described to exit processing unit and be connected between the anode of voltage source converter and negative terminal, or and it is connected in electricity Between the anode and negative terminal of Source Con-verters submodule；The semiconductor switch device conducting direction for exiting processing unit and stream DC current direction through voltage source converter is consistent, and cut-off shape is remained in voltage source converter normal course of operation；

It is characterized by: realizing that online failure of the voltage source converter unit in the operational process of direct current pole exits, include Following steps:

Step 1: after identifying that voltage source converter unit breaks down by detection electrical quantity and/or non-electric quantity, to The voltage source converter unit issues online failure and exits command；

Step 2: all semiconductor switch devices in processing unit that exit of voltage source converter unit to be retired are triggered Conducting is DC current (I_d) current channel is provided, while the voltage source being latched in voltage source converter unit to be retired changes Device is flowed, and the change of current corresponding to tripping voltage source converter unit to be retired becomes incoming switch；

Step 3: the unit bypass switch (S2) in voltage source converter unit to be retired is closed, electricity to be retired is flowed through DC current (the I of voltage source converter in Source Con-verters unit_d) it is transferred to unit bypass switch (S2)；

Step 4: be latched voltage source converter unit to be retired exits all semiconductor switch devices in processing unit, And pull open the switch of the cell isolation in voltage source converter unit to be retired (S1)；

Step 5: to voltage source converter unit to be retired carry out isolated operation, sequentially close unit bypass disconnecting link (D3), Unit bypass switch (S2) is pulled open, first unit isolation switch (D1) is pulled open, pulls open second unit isolation switch (D2), it is to be retired Voltage source converter unit exits completion.

During the above-mentioned online failure of voltage source converter unit exits, voltage source that other converter station correspondences need to exit Inverter unit normally exits process online according to it and carries out exiting operation accordingly.

The beneficial effects of the present invention are:

1, the present invention realizes DC transmission system DC by reasonable voltage source converter unit Topology Structure Design The online of single voltage source converter puts into and exits online when two or more inverter series operations of pole, meets series connection The operation and maintenance of type Hybrid HVDC system or tandem type flexible HVDC transmission system need.

2, tandem type Hybrid HVDC system or tandem type flexible direct current may be implemented in control method proposed by the present invention In transmission system voltage source converter it is online it is steady investment and exit, do not influence it is other operation inverters normal tables fortune Row.

Detailed description of the invention

Fig. 1 is the topology diagram of the first embodiment of voltage source converter unit of the present invention；

Fig. 2 is the topology diagram of the second embodiment of voltage source converter unit of the present invention；

Fig. 3 is the both ends bipolar series type Hybrid HVDC main loop using voltage source converter unit of the present invention Schematic diagram；

Fig. 4 is the both ends bipolar series type flexible HVDC transmission system major loop using voltage source converter unit of the present invention Schematic diagram；

Fig. 5 is the topological schematic diagram of voltage source converter in voltage source converter unit of the present invention, every mutually upper and lower bridge in figure Arm can be made of first kind sub-module cascade, or be made of first kind submodule and the second class submodule Mixed cascading；

Fig. 6 is the topology diagram of the 3rd embodiment of voltage source converter unit of the present invention；

Fig. 7 is the topology diagram of the fourth embodiment of voltage source converter unit of the present invention；

Fig. 8 is three-phase upper and lower bridge when voltage source converter output DC voltage is 0 in voltage source converter unit of the present invention The Voltage Reference wave waveform diagram of arm output；

Fig. 9 is three-phase alternating current when voltage source converter output DC voltage is 0 in voltage source converter unit of the present invention Voltage oscillogram；

Figure 10 is that a kind of voltage source converter unit being made of single semiconductor switch device of the invention exits processing The structural schematic diagram of device；

Figure 11 is a kind of voltage source converter list being composed in series by single semiconductor switch device and inductance of the invention Member exits the structural schematic diagram of processing unit；

Figure 12 is that a kind of voltage source converter unit being made of multiple semiconductor switch devices of the invention exits processing The structural schematic diagram of device；

Figure 13 is that a kind of voltage source converter unit being made of multiple semiconductor switch devices and inductance of the invention moves back The structural schematic diagram of processing unit out；

Figure 14 is the first the embodiment topological structure for the voltage source converter unit that processing unit is exited in present invention configuration Figure；

Figure 15 is second of embodiment topological structure of the voltage source converter unit that processing unit is exited in present invention configuration Figure；

Figure 16 is the third embodiment topological structure for the voltage source converter unit that processing unit is exited in present invention configuration Figure；

Figure 17 is the 4th kind of embodiment topological structure of the voltage source converter unit that processing unit is exited in present invention configuration Figure；

Figure 18 is that the both ends bipolar series type for the voltage source converter unit for exiting processing unit using present invention configuration is mixed Close DC transmission system major loop schematic diagram；

Figure 19 is that the both ends bipolar series type for the voltage source converter unit for exiting processing unit using present invention configuration is soft Property DC transmission system major loop schematic diagram；

Figure 20 is the first embodiment topology for the voltage source converter that processing unit is exited in configuration in submodule of the present invention Schematic diagram；

Figure 21 is second of embodiment topology for the voltage source converter that processing unit is exited in configuration in submodule of the present invention Schematic diagram.

Specific embodiment

Below with reference to drawings and the specific embodiments, technical solution of the present invention is described in detail.

The present invention provides a kind of voltage source converter unit topological structure and control method, for realizing DC transmission system The online of single voltage source converter puts into and moves back online when two or more voltage source converter series operations of direct current pole Out, operation and the maintenance needs of tandem type Hybrid HVDC system or tandem type flexible HVDC transmission system be can satisfy.

In order to achieve the above objectives, solution of the invention is:

The present invention provides a kind of voltage source converter unit topological structure for realizing the online investment of voltage source converter With exit online, the voltage source converter unit topological structure include by be serially connected first unit isolation switch (D1), Cell isolation switchs the series loop of (S1), voltage source converter, second unit isolation switch (D2) and connecting wire composition, on The beginning and end for stating series loop are respectively as the first direct current endpoint (X1) of the voltage source converter unit and the second direct current Endpoint (X2), for connecting with other voltage source converter units；Further include unit bypass disconnecting link (D3), is connected across institute It states between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Further include unit bypass switch (S2), is connected across described The nearly voltage source converter end (Y1) of first unit isolation switch (D1) and the nearly voltage source of second unit isolation switch (D2) change It flows between device end (Y2)；The series loop includes following two kinds of topological structures:

Topological structure i) the first direct current endpoint (X1) is successively through first unit isolation switch (D1), cell isolation switch (S1) It is connected to voltage source converter anode (Z1), the second direct current endpoint (X2) is connected to voltage source through second unit isolation switch (D2) Inverter negative terminal (Z2), as shown in Figure 1, it is suitable for configuring the voltage source converter unit in direct-flow positive pole；

Topological structure ii) the first direct current endpoint (X1) through first unit isolation switch (D1) is being connected to voltage source converter just It holds (Z1), the second direct current endpoint (X2) is successively connected to voltage through second unit isolation switch (D2), cell isolation switch (S1) Source inverter negative terminal (Z2), as shown in Fig. 2, it is suitable for configuring the voltage source converter unit in direct current cathode.

The both ends bipolar series type Hybrid HVDC main loop signal being made of above-mentioned voltage source converter unit Figure is as shown in Figure 3.

The both ends bipolar series type flexible HVDC transmission system major loop signal being made of above-mentioned voltage source converter unit Figure is as shown in Figure 4.

First kind submodule is the submodule that positive and negative zero three classes level can be exported under non-blocked state, such as full-bridge submodule Block (FBSM) etc..

Second class submodule be can only be exported under non-blocked state just, the submodule of zero liang of class level, such as half-bridge submodule Block (HBSM), class full-bridge submodule (SFBSM) etc..

In above scheme, the topological schematic diagram of voltage source converter is as shown in figure 5, wherein in voltage source converter unit U_ap、U_bp、U_cpThe respectively upper bridge arm voltage of voltage source converter A, B, C three-phase, U_an、U_bn、U_cnRespectively under A, B, C three-phase Bridge arm voltage.

Mode one, every mutually upper and lower bridge arm are made of first kind sub-module cascade, and which can guarantee voltage source converter The DC voltage that device can export as 0.

Mode two, every mutually upper and lower bridge arm are by first kind submodule, the second class submodule two types sub-module cascade The quantity configuration ratio of the mixing bridge arm of composition, each two seed module of bridge arm is identical, and specified in two types submodule capacitor In the identical situation of voltage, the quantity configuration ratio of first kind submodule is more than or equal to 50% in each bridge arm.Mode two is reduced The usage quantity of first kind submodule and still can to guarantee that voltage source converter can export be 0 in voltage source converter bridge arm DC voltage, reduce the design cost and running wastage of voltage source converter, have higher engineering application value.

It, can be according to actual needs in voltage in view of the loop resistance value of voltage source converter unit in above scheme is lower Current-limiting resistance is configured in the inverter unit of source, is changed to flow through voltage source in voltage source converter unit during moving back to online throwing The DC current of stream device carries out limitation control, and the voltage source converter unit for configuring current-limiting resistance includes: first be serially connected Cell isolation disconnecting link (D1), cell isolation switch (S1), voltage source converter, current-limiting resistance (R1), second unit isolation switch (D2) and connecting wire, first direct current endpoint of the beginning and end of the series loop respectively as the voltage source converter unit (X1) and the second direct current endpoint (X2), for connecting with other voltage source converter units；Unit bypass disconnecting link (D3), It is connected across between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Unit bypass switchs (S2), is connected across institute State the nearly voltage source of nearly the voltage source converter end (Y1) and second unit isolation switch (D2) of first unit isolation switch (D1) Between inverter end (Y2)；Resistance by-pass switch (S3) is in parallel with current-limiting resistance (R1)；The series loop includes following Two kinds of topological structures:

I) the first direct current endpoint (X1) is successively connected to electricity through first unit isolation switch (D1), cell isolation switch (S1) Source Con-verters anode (Z1), the second direct current endpoint (X2) successively connect through second unit isolation switch (D2), current-limiting resistance (R1) It is connected to voltage source converter negative terminal (Z2), as shown in fig. 6, it is suitable for configuring the voltage source converter unit in direct-flow positive pole；

Ii) the first direct current endpoint (X1) is successively connected to voltage through first unit isolation switch (D1), current-limiting resistance (R1) Source inverter anode (Z1), the second direct current endpoint (X2) is successively through second unit isolation switch (D2), cell isolation switch (S1) It is connected to voltage source converter negative terminal (Z2), as shown in fig. 7, it is suitable for configuring the voltage source converter list in direct current cathode Member.

The present invention also provides a kind of control methods of voltage source converter unit topological structure for realizing the voltage source Online investment of the voltage source converter unit of inverter unit topological structure in the operational process of direct current pole, specifically comprising following Step:

Step 1: receive issue voltage source converter unit investment order, treat investment voltage source converter unit into Row attended operation sequentially closes second unit isolation switch (D2), closes first unit isolation switch (D1), closes unit bypass Switch (S2) pulls open unit bypass disconnecting link (D3)；For being configured with the voltage source converter unit to be put into of current-limiting resistance, current limliting Resistance is initially set investment state i.e. resistance by-pass switch (S3) and is in quartile；

Step 2: it closes the change of current corresponding to voltage source converter unit to be put into and becomes incoming switch and to the inverter list Member, which is exchanged, does not control charging, starts charge control after exchanging and not controlling charging complete, by the capacitance voltage of each bridge arm submodule It is charged to close to rated value；

Step 3: voltage source converter unit to be put into sets the voltage source converter unit under constant voltage control mode DC voltage instruction value (the U of middle voltage source converter_d-ord) be 0 and unlock the voltage source converter, it is acted in voltage controller DC voltage (the U of lower voltage source converter output_d) control is 0, the operating status of the voltage source converter at this time are as follows: each bridge The Voltage Reference wave that first kind submodule normal release and output in arm match with alternating voltage, every mutually upper and lower bridge arm are defeated Voltage Reference wave amplitude out is equal and opposite in phase, as being configured with the second class submodule in voltage source converter bridge arm, then Two class submodules, which bypass, to be exited；Voltage Reference wave waveform such as Fig. 8 institute of the upper and lower bridge arm output of the voltage source converter at this time Show, wherein U_an-ref、U_bn-ref、U_cn-refThe respectively Voltage Reference wave of voltage source converter A, B, C three-phase lower bridge arm, U_ap-ref、U_bp-ref、U_cp-refThe Voltage Reference wave of bridge arm, U respectively on A, B, C three-phase_dFor the straight of voltage source converter output Galvanic electricity pressure；The corresponding three-phase alternating current corrugating of the voltage source converter is as shown in figure 9, wherein U at this time_a、U_b、U_cRespectively A, B, the alternating voltage of C three-phase.

Step 4: the cell isolation switch (S1) for closing voltage source converter unit to be put into completes the voltage source converter The electrical connection of voltage source converter in unit, the control model of the voltage source converter is smoothly switched as constant current control side Formula and the DC current instruction value (I for setting the voltage source converter_d-ord) be working voltage source inverter DC current reality Border measured value, under current controller effect, when the DC current for flowing through voltage source converter in the voltage source converter unit (I_d) be adjusted to and pull open unit bypass switch when inverter DC current actual measured value in working voltage source is of substantially equal (S2)；For being configured with the voltage source converter unit of current-limiting resistance, closed by resistance after unit bypass switch (S2) pulls open Way switch (S3) exits current-limiting resistance (R1)；

Step 5: converter station where voltage source converter unit such as to be put into is DC voltage control station, then will be wait put into The control model of voltage source converter smoothly switches as constant voltage control mode and sets the voltage in voltage source converter unit DC voltage instruction value (the U of source inverter_d-ord) it is operational objective value, the voltage source converter list under voltage controller effect Voltage source converter steps up the DC voltage (U of output in member_d) operational objective value risen to certain rate ramp；Such as Converter station where voltage source converter unit to be put into is DC current control station or dc power control station, then will electricity be put into The control model of voltage source converter remains constant current control mode and sets the voltage source converter in Source Con-verters unit DC current instruction value (the I of device_d-ord) flowed under current controller effect for the DC current operational objective value of this direct current pole DC current (I through voltage source converter in the voltage source converter unit_d) it is adjusted to the DC current operation of this direct current pole Target value；Later, voltage source converter unit investment to be put into is completed.

For two-terminal direct current transmission system, the control model generallyd use is one end converter station control DC current or direct current Power, other end converter station control DC voltage, and both ends cooperation makes direct current transmission power maintain target value, and control model can be with It is converted between the converter station of both ends.

During being put into online using the voltage source converter unit of the voltage source converter unit topological structure, press According to the first voltage source converter unit of investment DC current control station or dc power control station, then put into DC voltage control station Voltage source converter unit sequence carry out voltage source converter unit online investment operate.

The present invention also provides a kind of control methods of voltage source converter unit topological structure for realizing the voltage source Online in the operational process of direct current pole of the voltage source converter unit of inverter unit topological structure normally exits, and specifically includes Following steps:

Step 1: receiving the voltage source converter unit issued and exit command, such as voltage source converter unit institute to be retired It is DC voltage control station in converter station, then the control model of voltage source converter is kept in voltage source converter unit to be retired For constant voltage control mode and set the DC voltage instruction value (U of the voltage source converter_d-ord) it is 0, make in voltage controller DC voltage (the U exported with voltage source converter in the lower voltage source converter unit_d) dropped to certain rate ramp 0；The converter station as where voltage source converter unit to be retired is DC current control station or dc power control station, then first will be to The control model for exiting voltage source converter in voltage source converter unit is smoothly switched by constant current control mode as constant voltage Control mode and the DC voltage instruction value (U for setting the voltage source converter_d-ord) it is 0, it should under the action of voltage controller DC voltage (the U that voltage source converter exports in voltage source converter unit_d) with certain rate ramp drop to 0；When to Exit the DC voltage (U that voltage source converter exports in voltage source converter unit_d) when dropping to 0, the voltage source converter Operating status are as follows: first kind submodule in each bridge arm keeps normal release and exports the voltage to match with alternating voltage joining Examine wave, the Voltage Reference wave amplitude of every mutually upper and lower bridge arm output is equal and opposite in phase, as configured in voltage source converter bridge arm Second class submodule, then the second class submodule bypasses exits.

Step 2: the unit bypass switch (S2) of voltage source converter unit to be retired is closed, the voltage source is flowed through and changes Flow the DC current (I of voltage source converter in device unit_d) it is transferred to unit bypass switch (S2)；For being configured with current-limiting resistance Voltage source converter unit, unit bypass switch (S2) close after, pull open resistance by-pass switch (S3) investment current-limiting resistance (R1)；

Step 3: it pulls open the cell isolation switch (S1) of voltage source converter unit to be retired and is latched the voltage source converter Voltage source converter in device unit；

Step 4: isolated operation is carried out to voltage source converter unit to be retired, sequentially performs the following operations: pulling open wait move back The change of current corresponding to voltage source converter unit becomes incoming switch, closes unit bypass disconnecting link (D3), pulls open unit bypass and open out (S2) is closed, first unit isolation switch (D1) is pulled open, pulls open second unit isolation switch (D2), completes voltage source converter to be retired The electrical isolation of voltage source converter in device unit, voltage source converter unit to be retired exit completion.

Process is normally being exited using the voltage source converter unit of the voltage source converter unit topological structure online In, according to first exiting the voltage source converter unit at DC voltage control station, then exit DC current control station or dc power The sequence of the voltage source converter unit of control station carries out the online of voltage source converter unit and normally exits operation.

When single voltage source converter breaks down, the full-controlled switch device of voltage source converter needs quick lock With isolated fault, this causes voltage source converter to lose normal control ability, can not be using the above-mentioned control normally exited online The online failure that method carries out voltage source converter exits.Through studying, place is exited by configuring in voltage source converter unit The online failure that voltage source converter may be implemented in reason device exits, and exiting processing unit includes: at least one semiconductor switch Device or at least one semiconductor switch device and an inductance, the semiconductor switch device and the inductance series connection and At；Described device is simultaneously connected between the anode of voltage source converter and negative terminal, or and is connected in voltage source converter submodule Between the anode and negative terminal of block (SM).

The semiconductor switch device conducting direction for exiting processing unit and the DC current for flowing through voltage source converter Direction is consistent, and off state is remained in voltage source converter normal course of operation, is not influencing DC transmission system just Often operation；The semiconductor switch device is half control type switching device, such as thyristor (SCR) or full-controlled switch device, such as IGBT, IGCT, IEGT, GTO etc..

The voltage source converter unit that Figure 10 show a kind of single semiconductor switch device exits the structure of processing unit Schematic diagram, in parallel with voltage source converter for described device comprising the first terminal 1, second in parallel terminal 2 in parallel, 3 be half Conductor switching device.

Figure 11 show a kind of voltage source converter unit being made of single semiconductor switch device and inductance and exits place The structural schematic diagram for managing device is used for described device and voltage source converter comprising the first terminal 1, second in parallel terminal 3 in parallel Parallel connection, the semiconductor switch device 4 cathode (if half control type switching device, then referred to as cathode, if full-controlled switch Device is then known as emitter, is related to cathode if following, identical) 2 are series at inductance 5.The inductance 5 can be single electricity Sense, can also be connected and/or be formed in parallel by multiple inductance.

Figure 12 show a kind of voltage source converter unit being made of multiple semiconductor switch devices and exits processing unit Structural schematic diagram, it is in parallel with voltage source converter for described device comprising the first terminal 1, second in parallel terminal 4 in parallel, Described device is by multiple semiconductor switch device shapes including but not limited to semiconductor switch device 5 and semiconductor switch device 6 At the anode of the cathode of semiconductor switch device 5 and next semiconductor switch device (if half control type switching device, then claims For anode, then it is known as collector if full-controlled switch device, is related to anode if following, identical) 2 are connected in, semiconductor is opened The cathode of the anode and a upper semiconductor switch device that close device 6 is connected in 3.All semiconductor switch devices in described device It is all made of same trigger pulse, is triggered conducting, is simultaneously turned off when branch current is reduced to 0, or same in synchronization Moment is triggered shutdown.

Figure 13 show a kind of voltage source converter unit being made of multiple semiconductor switch devices and inductance and exits place The structural schematic diagram for managing device is used for described device and voltage source converter comprising the first terminal 1, second in parallel terminal 5 in parallel Parallel connection, described device is by multiple semiconductor switch including but not limited to semiconductor switch device 6 and semiconductor switch device 7 Device is connected formation with inductance 8, and the anode of the cathode of semiconductor switch device 6 and next semiconductor switch device is connected in 2, The cathode of the anode of semiconductor switch device 7 and a upper semiconductor switch device is connected in 3, the yin of semiconductor switch device 7 Pole and inductance 8 are connected in 4.The inductance 8 can be single inductance, can also be connected and/or is formed in parallel by multiple inductance.Institute All semiconductor switch devices stated in device are all made of same trigger pulse, are triggered conducting in synchronization, in branch electricity Stream simultaneously turns off when being reduced to 0, or is triggered shutdown in synchronization.

It is described when exiting processing unit and being connected between voltage source converter anode (Z1) and negative terminal (Z2), the voltage Source inverter unit includes following four kinds of topological structures:

I) structure shown in Figure 14 is suitable for the voltage source converter unit configured in converting plant direct-flow positive pole, exits processing The conducting direction of semiconductor switch device is that Z2 is directed toward Z1 in device, with the DC current (I for flowing through voltage source converter_d) direction Unanimously；

Ii) structure shown in Figure 15 is suitable for the voltage source converter unit configured in Inverter Station direct-flow positive pole, exits place The conducting direction for managing semiconductor switch device in device is that Z1 is directed toward Z2, with the DC current (I for flowing through voltage source converter_d) side To consistent；

Iii) structure shown in Figure 16 is suitable for the voltage source converter unit configured in converting plant direct current cathode, exits place The conducting direction for managing semiconductor switch device in device is that Z2 is directed toward Z1, with the DC current (I for flowing through voltage source converter_d) side To consistent；

Iv) structure shown in Figure 17 is suitable for the voltage source converter unit configured in Inverter Station direct current cathode, exits place The conducting direction for managing semiconductor switch device in device is that Z1 is directed toward Z2, with the DC current (I for flowing through voltage source converter_d) side To consistent.

Figure 18 show and exits the both ends bipolar series that the voltage source converter unit of processing unit forms described in configuration Type Hybrid HVDC main loop schematic diagram, DC current direction flows to voltage source converter by thyristor transverter converter station Device converter station.

Figure 19 show and exits the both ends bipolar series that the voltage source converter unit of processing unit forms described in configuration Type flexible HVDC transmission system major loop schematic diagram, DC current direction flows to voltage source by voltage source converter converter station 1 and changes Flow device converter station 2.

It is described when exiting processing unit and being connected between voltage source converter submodule anode (A) and negative terminal (B), it is described Voltage source converter in voltage source converter unit includes following two kinds of topological structures:

I) structure shown in Figure 20 is suitable for configuring the voltage source converter in converting plant direct-flow positive pole and cathode, exits place The conducting direction for managing semiconductor switch device in device is that B is directed toward A, with the DC current (I for flowing through voltage source converter_d) direction Unanimously；

Ii) structure shown in Figure 21 is suitable for configuring the voltage source converter in Inverter Station direct-flow positive pole and cathode, exits The conducting direction of semiconductor switch device is that A is directed toward B in processing unit, with the DC current (I for flowing through voltage source converter_d) side To consistent.

A phase can be selected in the three-phase bridge arm of voltage source converter in practical engineering applications, by the mutually upper and lower bridge Each submodule of arm, which configures, exits processing unit, remaining two-phase does not configure, to reduce the usage quantity of semiconductor switch device.

It should be noted that can be adopted with the tandem type flexible HVDC transmission system of two-way flow for DC current It is configured with the mode for exiting two groups processing unit reverse parallel connection, guarantees the equal energy under two current directions of forward and reverse Realize that voltage source converter unit exits online.

It, can be in above-mentioned voltage source converter list for being configured with the voltage source converter unit for exiting processing unit Step A is added between the step of first online normal withdrawal control method one and step 2: by voltage source converter unit to be retired All semiconductor switch device triggering and conductings that exit in processing unit be DC current (I_d) current channel is provided；In step Step B is added between rapid three and step 4: being latched exiting for voltage source converter unit to be retired and all in processing unit partly leads Body switching device；The technological merit for increasing above-mentioned steps is: can guarantee the voltage source converter unit to be retired in step 2 Unit bypass switch (S2) close before voltage source converter output DC voltage (U_d) it is 0, so that unit bypass is switched (S2) Has combined floodgate condition.

Processing method is exited the present invention also provides a kind of voltage source converter unit topological structure, for realizing institute is used Online failure of the voltage source converter unit of voltage source converter unit topological structure in the operational process of direct current pole is stated to exit, Comprising the following steps:

Step 1: after identifying that voltage source converter unit breaks down by detection electrical quantity and/or non-electric quantity, to The inverter unit issues online failure and exits command；

Step 5: isolated operation is carried out to voltage source converter unit to be retired, sequentially performs the following operations: closing unit By-pass knife switch (D3) pulls open unit bypass switch (S2), pulls open first unit isolation switch (D1), pulls open second unit isolation knife Lock (D2) completes the electrical isolation of voltage source converter in voltage source converter unit to be retired, voltage source converter to be retired Unit exits completion.

Process is being exited using the online failure of voltage source converter unit of the voltage source converter unit topological structure In, the voltage source converter unit that other converter station correspondences need to exit normally exits method according to it online and is exited accordingly Operation.

It should be noted that the switch, the knife that are configured in voltage source converter unit topological structure embodiment of the present invention The equipment such as lock are necessary configuration, are suitably increased on this basis and adjustment is also fallen within the scope of the present invention.

The above examples only illustrate the technical idea of the present invention, and this does not limit the scope of protection of the present invention, all According to the technical idea provided by the invention, any changes made on the basis of the technical scheme each falls within the scope of the present invention Within.

Claims

1. a kind of control method of voltage source converter unit topological structure, the voltage source converter unit topological structure include By first unit isolation switch (D1), cell isolation switch (S1), voltage source converter, second unit isolation knife being serially connected The series loop that lock (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop are respectively as the voltage source converter The the first direct current endpoint (X1) and the second direct current endpoint (X2) of unit, for connecting with other voltage source converter units； Further include unit bypass disconnecting link (D3), is connected across between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Also Including unit bypass switch (S2), be connected across the first unit isolation switch (D1) nearly voltage source converter end (Y1) and Between the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

Topological structure i) the first direct current endpoint (X1) is successively through first unit isolation switch (D1), cell isolation switch (S1) connection To voltage source converter anode (Z1), the second direct current endpoint (X2) is connected to voltage source converter through second unit isolation switch (D2) Device negative terminal (Z2)；

Topological structure ii) the first direct current endpoint (X1) through first unit isolation switch (D1) is connected to voltage source converter anode (Z1), the second direct current endpoint (X2) is successively connected to voltage source through second unit isolation switch (D2), cell isolation switch (S1) Inverter negative terminal (Z2)；

It is characterized by: realizing online investment of the voltage source converter unit in the operational process of direct current pole comprising the steps of:

Step 1: the voltage source converter unit investment order issued is received, investment voltage source converter unit is treated and is connected Operation is connect, second unit isolation switch (D2) is sequentially closed, closes first unit isolation switch (D1), closes unit bypass switch (S2), unit bypass disconnecting link (D3) is pulled open；

Step 2:, which closing the change incoming switch of the change of current corresponding to voltage source converter unit to be put into, and treats investment voltage source changes The voltage source converter flowed in device unit carries out charge control, by the voltage source converter in voltage source converter unit to be put into The capacitance voltage of each bridge arm submodule is charged to close to rated value；

Step 3: unlocking the voltage source converter in voltage source converter unit to be put into and controls the DC voltage of its output (U_d) it is 0；

Step 4: closing the cell isolation switch (S1) in voltage source converter unit to be put into, and control flows through voltage to be put into DC current (the I of voltage source converter in the inverter unit of source_d) practical to the DC current with working voltage source inverter When measured value is of substantially equal, the unit bypass switch (S2) in voltage source converter unit to be put into is pulled open；

Step 5: converter station where voltage source converter unit such as to be put into is DC voltage control station, then controls electricity to be put into DC voltage (the U that voltage source converter exports in Source Con-verters unit_d) to operational objective value；

Converter station where voltage source converter unit such as to be put into is DC current control station or dc power control station, then controls Flow through the DC current (I of voltage source converter in voltage source converter unit to be put into_d) to operational objective value；

Later, voltage source converter unit investment to be put into is completed.

2. a kind of control method of voltage source converter unit topological structure as described in claim 1, it is characterised in that: step It is described to control the DC voltage (U that voltage source converter exports in voltage source converter unit to be put into three_d) be 0 control Method specifically includes, by the first kind submodule normal release in each bridge arm of the voltage source converter and output and alternating voltage The Voltage Reference wave amplitude of the Voltage Reference wave to match, every mutually upper and lower bridge arm output is equal and opposite in phase, if voltage source The second class submodule is configured in converter bridge arm, then the second class submodule, which bypasses, exits；

Wherein, the first kind submodule is the submodule that positive and negative zero three classes level can be exported under non-blocked state, described Second class submodule be can only be exported under non-blocked state just, the submodule of zero liang of class level.

3. a kind of control method of voltage source converter unit topological structure as described in claim 1, it is characterised in that: in institute It states during voltage source converter unit puts into online, according to the electricity for first putting into DC current control station or dc power control station Source Con-verters unit, put into again DC voltage control station voltage source converter unit sequence carry out voltage source converter list The online investment operation of member.

4. a kind of control method of voltage source converter unit topological structure, the voltage source converter unit topological structure include By first unit isolation switch (D1), cell isolation switch (S1), voltage source converter, second unit isolation knife being serially connected The series loop that lock (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop are respectively as the voltage source converter The the first direct current endpoint (X1) and the second direct current endpoint (X2) of unit, for connecting with other voltage source converter units； Further include unit bypass disconnecting link (D3), is connected across between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Also Including unit bypass switch (S2), be connected across the first unit isolation switch (D1) nearly voltage source converter end (Y1) and Between the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

It include following it is characterized by: realizing that online in the operational process of direct current pole of voltage source converter unit normally exits Step:

Step 1: receiving the voltage source converter unit issued and exit command, and controls electric in voltage source converter unit to be retired DC voltage (the U of Source Con-verters output_d) drop to 0；

Step 2: the unit bypass switch (S2) in voltage source converter unit to be retired is closed, voltage source to be retired is flowed through The DC current of voltage source converter is transferred to unit bypass switch (S2) in inverter unit；

Step 3: it pulls open the cell isolation switch (S1) in voltage source converter unit to be retired and is latched voltage source to be retired and change Flow the voltage source converter in device unit；

Step 4: isolated operation is carried out to voltage source converter unit to be retired, is sequentially to pull open voltage source converter to be retired The change of current corresponding to unit becomes incoming switch, closes unit bypass disconnecting link (D3), pull open unit bypass switch (S2), pull open first Cell isolation disconnecting link (D1) pulls open second unit isolation switch (D2), and voltage source converter unit to be retired exits completion.

5. a kind of control method of voltage source converter unit topological structure as claimed in claim 4, it is characterised in that: step In one, the DC voltage (U of voltage source converter output in the control voltage source converter unit to be retired_d) drop to 0 Method is specifically included the first kind submodule holding normal release and output and alternating current in each bridge arm of the voltage source converter Press the Voltage Reference wave that matches, the Voltage Reference wave amplitude of every mutually upper and lower bridge arm output is equal and opposite in phase, if voltage The second class submodule is configured in the converter bridge arm of source, then the second class submodule, which bypasses, exits；

6. a kind of control method of voltage source converter unit topological structure as claimed in claim 4, it is characterised in that: in institute It states during voltage source converter unit normally exits online, according to the voltage source converter list for first exiting DC voltage control station Member, the sequence for the voltage source converter unit for exiting DC current control station or dc power control station again carry out voltage source converter The online of device unit normally exits operation.

7. a kind of control method of voltage source converter unit topological structure as claimed in claim 4, it is characterised in that:

The voltage source converter unit topological structure further include formed by least one semiconductor switch device exit processing Device；It is described to exit processing unit and be connected between the anode of voltage source converter and negative terminal, or and it is connected in voltage source Between the anode and negative terminal of inverter submodule；The semiconductor switch device conducting direction for exiting processing unit and flow through electricity The DC current direction of Source Con-verters is consistent, and cut-off shape is remained in voltage source converter normal course of operation；

Normally exit process for being configured with the online of voltage source converter unit for exiting processing unit, step 1 with Further include step A between step 2: voltage source converter unit to be retired is exited into all semiconductor switch in processing unit Device triggering and conducting is DC current (I_d) current channel is provided；

Further include step B between step 3 and step 4: be latched voltage source converter unit to be retired exits processing unit In all semiconductor switch devices.

8. a kind of control method of voltage source converter unit topological structure, the voltage source converter unit topological structure include By first unit isolation switch (D1), cell isolation switch (S1), voltage source converter, second unit isolation knife being serially connected The series loop that lock (D2) and connecting wire are constituted, the beginning and end of above-mentioned series loop are respectively as the voltage source converter The the first direct current endpoint (X1) and the second direct current endpoint (X2) of unit, for connecting with other voltage source converter units； Further include unit bypass disconnecting link (D3), is connected across between the first direct current endpoint (X1) and the second direct current endpoint (X2)；Also Including unit bypass switch (S2), be connected across the first unit isolation switch (D1) nearly voltage source converter end (Y1) and Between the nearly voltage source converter end (Y2) of second unit isolation switch (D2)；

The series loop includes following two kinds of topological structures:

It is characterized by: realizing that online failure of the voltage source converter unit in the operational process of direct current pole exits, comprising following Step:

Step 1: after identifying that voltage source converter unit breaks down by detection electrical quantity and/or non-electric quantity, to the electricity Source Con-verters unit issues online failure and exits command；

Step 2: voltage source converter unit to be retired is exited into all semiconductor switch device triggering and conductings in processing unit For DC current (I_d) current channel, while the voltage source converter being latched in voltage source converter unit to be retired are provided Device, and the change of current corresponding to tripping voltage source converter unit to be retired becomes incoming switch；

Step 3: the unit bypass switch (S2) in voltage source converter unit to be retired is closed, voltage source to be retired is flowed through DC current (the I of voltage source converter in inverter unit_d) it is transferred to unit bypass switch (S2)；

Step 4: be latched voltage source converter unit to be retired exits all semiconductor switch devices in processing unit, and draws Open the cell isolation switch (S1) in voltage source converter unit to be retired；

Step 5: isolated operation is carried out to voltage source converter unit to be retired, unit bypass disconnecting link (D3) is sequentially closed, pulls open Unit bypass switch (S2) pulls open first unit isolation switch (D1), pulls open second unit isolation switch (D2), voltage to be retired Source inverter unit exits completion.

9. a kind of control method of voltage source converter unit topological structure as claimed in claim 8, it is characterised in that: in institute State during the online failure of voltage source converter unit exits, the voltage source converter unit that other converter station correspondences need to exit by Method is normally exited online according to it to carry out exiting operation accordingly.