CN108933434A - A kind of flexible direct current transmission converter station failure current limit protection system and method - Google Patents
A kind of flexible direct current transmission converter station failure current limit protection system and method Download PDFInfo
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- CN108933434A CN108933434A CN201810833039.XA CN201810833039A CN108933434A CN 108933434 A CN108933434 A CN 108933434A CN 201810833039 A CN201810833039 A CN 201810833039A CN 108933434 A CN108933434 A CN 108933434A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention discloses a kind of flexible direct current transmission converter station failure current limits to protect system and method, and the AC system in system is connected by alternating current circuit with the side that exchanges of voltage source converter；Measuring unit is arranged at the point of common coupling that AC system is connected with voltage source converter, is connected with control system, and control system is connect with voltage source converter.The current electrical quantity of measuring unit real-time monitoring AC system, when judging that AC system breaks down, by control system according to current electrical quantity switching control mode, it is operated by voltage source converter according to the change of current that the instruction of control system carries out AC and DC, it realizes the control to voltage source converter exchange side electric voltage frequency, and then achievees the purpose that inhibit AC system electric current out-of-limit.As it can be seen that system and method provided in this embodiment, can when realizing fault in ac transmission system fault current limiting, while the damage to voltage source converter can be reduced, improve the operation stability of electric system.
Description
Technical field
The present invention relates to flexible DC transmission technology field more particularly to a kind of flexible direct current transmission converter station failure current limits
Protect system and method.
Background technique
In recent years, flexible straight as the demand that the new-energy grid-connecteds such as photovoltaic, wind-powered electricity generation and passive network are powered is continuously improved
Stream technology of transmission of electricity provides a kind of important channel for new-energy grid-connected and passive network power supply, gradually attracts attention.Flexible direct current
For technology of transmission of electricity based on voltage source converter, voltage source converter DC side uses capacitor burning voltage, and exchange side is adopted
AC system is controlled with change of current reactance.
And when AC system breaks down, since the IGBT of voltage source converter is difficult to bear overcurrent, usually adopt
Take the measure that alternating current circuit is cut off after being latched inverter.But be latched inverter and restore the process that inverter operates normally, meeting
DC voltage larger fluctuation is caused, system stability is affected.As it can be seen that existing fault protecting method easily influences system operation
Stability.
Summary of the invention
The present invention provides a kind of flexible direct current transmission converter station failure current limits to protect system and method, existing to solve
Fault protecting method easily influences the problem of system run all right.
In a first aspect, the present invention provides a kind of flexible direct current transmission converter station failure current limits to protect system, comprising: exchange
System, voltage source converter, control system and measuring unit；Wherein,
The AC system is connected by alternating current circuit with the side that exchanges of the voltage source converter；
The measuring unit is arranged at the point of common coupling that AC system is connected with voltage source converter, measuring unit
Output end and control system input terminal connect；Measuring unit is used to monitor the current electrical quantity of AC system, and, it will supervise
The current electrical quantity measured is delivered to control system；
The output end of the control system and the input terminal of voltage source converter connect, and the control system is for docking
The current electrical quantity received is handled, and the voltage source converter is delivered to after processing, controls the voltage-source type
The alternating voltage and alternating current of inverter inside；
The DC side of the voltage source converter is connected with direct current system, realizes the change of current of AC system and direct current system
Operation.
Optionally, the voltage source converter includes several exchange change of current reactance, six bridge arm change of current structure of several three-phases
With several DC capacitors；The six bridge arm change of current structure of three-phase is connect with direct current system, and each six bridge arm change of current structure of three-phase is
Parallel-connection structure；
One end of each exchange change of current reactance is connected to the middle part of six bridge arm change of current structure of three-phase, each described
The other end of exchange change of current reactance passes through a resistance respectively and connect with AC system；
The junction of exchange change of current reactance and six bridge arm change of current structure of three-phase is arranged in the DC capacitor.
Optionally, the six bridge arm change of current structure of three-phase is symmetrical structure；Six bridge arm change of current structure of three-phase includes several bridges
Arm reactance and several change of current submodules are successively gone here and there along the middle part of six bridge arm change of current structure of three-phase to the position connecting with direct current system
Join a bridge arm reactance and several change of current submodules.
Optionally, the control system includes station level control module and valve grade control module, the station level control module
Input terminal and the output end of measuring unit connect, and for handling the current electrical quantity that measuring unit monitors, are adjusted
Wave processed is delivered to valve grade control module；
The output end of the valve grade control module and the input terminal of voltage source converter connect, and valve grade control module is used for
Modulating wave is modulated, control instruction is obtained and voltage source converter is controlled.
Optionally, the station level control module includes outer ring current control unit and inner ring current control unit；It is described outer
Circular current control unit and inner ring current control unit are modulated for calculating current electrical quantity and preset reference value
Wave is delivered to valve grade control module.
Optionally, the AC system includes passive network, wind-powered electricity generation energy network or photovoltaic energy network.
Second aspect, the present invention also provides a kind of flexible direct current transmission converter station failure current limit guard method, the sides
Method includes:
The current electrical quantity of measuring unit real-time monitoring AC system judges that AC system is according to the current electrical quantity
It is no that electric current occur out-of-limit；
If it is out-of-limit that electric current occurs in the alternating current circuit, the current electrical quantity is sent to control system by measuring unit；
The control system is according to the current electrical quantity switching control mode received, according to the controlling party after switching
Formula generates current control instruction；And the current control instruction is sent to voltage source converter；
The voltage source converter inhibits the alternating current of AC system according to current control instruction, realizes exchange system
The change of current of system and direct current system operates.
Optionally, the control system includes station level control module and valve grade control module；And it controls as steps described below
System processed generates current control according to the current electrical quantity switching control mode received, according to the control mode after switching
Instruction:
The station level control module controls current electrical quantity and default electrical quantity and inner ring current control in outer circular current
In calculated, obtain target modulation wave, be delivered to valve grade control module；
The valve grade control module is modulated processing to target modulation wave, dynamic according to modulation treatment result starting protection
Make, control mode is switched to active reactive control mode；And according to the active reactive control mode, generate current control
System instruction.
Optionally, the voltage source converter inhibits AC system according to current control instruction as steps described below
Alternating current:
According to the current control instruction, the loop integrator controlled in the voltage source converter is reset；
According to the active reactive control mode, alternating voltage and alternating current in voltage source converter are controlled；
According to the alternating voltage and alternating current in the voltage source converter after control, working as at point of common coupling is adjusted
Preceding electrical quantity inhibits the alternating current of AC system；Wherein, the current electrical quantity includes active power and reactive power.
Optionally, further includes:
After completing primary current control process, the control system is restored control mode by active reactive control mode
To width phase control mode；
According to the new current electrical quantity that the measuring unit monitors, judge that the AC system is out-of-limit with the presence or absence of electric current；
If that there are electric currents is out-of-limit for the AC system, cutting instruction is generated by the control system and being sent to voltage-source type
Inverter, to cut off the connection of voltage source converter and AC system.
From the above technical scheme, a kind of flexible direct current transmission converter station failure current limit provided in an embodiment of the present invention is protected
Protecting system and method, the system include AC system, voltage source converter, control system and measuring unit；AC system is logical
Alternating current circuit is crossed to be connected with the side that exchanges of voltage source converter；Measuring unit is arranged in AC system and voltage source converter
At the point of common coupling of connection, it is connected with control system, control system is connect with voltage source converter.Measuring unit is supervised in real time
The current electrical quantity of test cross streaming system is switched by control system according to current electrical quantity when judging that AC system breaks down
Control mode is operated according to the change of current that the instruction of control system carries out AC and DC by voltage source converter, is realized to electricity
Potential source type inverter exchanges the control of side electric voltage frequency, and then achievees the purpose that inhibit AC system electric current out-of-limit.As it can be seen that this reality
The system and method for example offer is provided, can when realizing fault in ac transmission system fault current limiting, while can reduce to voltage-source type
The damage of inverter improves the operation stability of electric system.
Detailed description of the invention
In order to illustrate more clearly of technical solution of the present invention, letter will be made to attached drawing needed in the embodiment below
Singly introduce, it should be apparent that, for those of ordinary skills, without any creative labor,
It is also possible to obtain other drawings based on these drawings.
Fig. 1 is the structural representation that flexible direct current transmission converter station failure current limit provided in an embodiment of the present invention protects system
Figure；
Fig. 2 is the flow chart of flexible direct current transmission converter station failure current limit guard method provided in an embodiment of the present invention；
Fig. 3 is the schematic diagram of flexible direct current transmission converter station failure current limit protection system when breaking down；
Fig. 4 (a) (b) (c) (d) (e) is flexible direct current transmission converter station failure current limit protection system when breaking down
Dynamic Simulation Results figure.
It illustrates:
Wherein, 1- AC system, 2- measuring unit, 3- control system, 31- station level control module, 32- valve grade control mould
Block, 4- voltage source converter, 5- direct current system.
Specific embodiment
Fig. 1 is the structural representation that flexible direct current transmission converter station failure current limit provided in an embodiment of the present invention protects system
Figure.
Referring to Fig. 1, flexible direct current transmission converter station failure current limit provided in an embodiment of the present invention protects system, is applied to soft
Property direct-current transmission converter station break down the case where, the protection system include: AC system 1, voltage source converter 4, control
System 3 and measuring unit 2；Wherein,
AC system 1 is connected by alternating current circuit with the side that exchanges of voltage source converter 4；In the present embodiment, exchange system
System includes passive network, wind-powered electricity generation energy network or photovoltaic energy network, and such network is new energy network, beneficial to environmental protection.
At the point of common coupling that AC system 1 is arranged in measuring unit 2 and voltage source converter 4 connects, measuring unit 2
Output end connect with the input terminal of control system 3；Measuring unit 2 is used to monitor the current electrical quantity of AC system 1, and,
The current electrical quantity monitored is delivered to control system 3.
The current electrical quantity of 2 real-time monitoring AC system 1 of measuring unit, i.e. alternating current Is, alternating voltage Upcc, it is active
Power P and reactive power Q.Judge whether AC system 1 breaks down according to the data monitored, i.e., whether electric current occurs and get over
Situations such as limit, three-phase shortcircuit.
Measuring unit 2 is secondary device, is not connected directly with alternating current circuit.Measuring unit 2 is by the above-mentioned items detected
Data are transmitted to control system 3, straight to guarantee so that control system 3 is precisely controlled according to the real time data of AC system 1
The operation stability of streaming system and AC system.
The output end of control system 3 is connect with the input terminal of voltage source converter 4, and control system 3 is used for receiving
Current electrical quantity handled, be delivered to voltage source converter 4 after processing, control the friendship inside voltage source converter 4
Galvanic electricity pressure and alternating current.
The current electrical quantity that control system 3 sends measuring unit 2 is handled, and generates control instruction after processing, and
It is sent to voltage source converter 4, to control the alternating voltage and alternating current inside voltage source converter 4, so that voltage
The electric current of electric current and AC system 1 inside source type inverter 4, which carries out the change of current, can pass through this when AC system 1 breaks down
Method carries out the change of current, restores AC system 1 normally, meanwhile, the voltage stability of voltage source converter 4 is not influenced, is improved
The stability of Operation of Electric Systems.
In order to which the current electrical quantity more accurately sent to measuring unit 2 is handled, in the present embodiment, control system
3 include station level control module 31 and valve grade control module 32, the input terminal and the output end of measuring unit 2 of station level control module 31
Connection, for handling the current electrical quantity that measuring unit 2 monitors, obtains modulating wave, is delivered to valve grade control module
32。
Wherein, station level control module 31 includes outer ring current control unit and inner ring current control unit；Outer circular current control
Unit processed and inner ring current control unit obtain modulating wave and are delivered to for calculating current electrical quantity and preset reference value
Valve grade control module 32.
In the present embodiment, preset reference value is that the AC system 1 that measuring unit 2 monitors is electrical when not breaking down
Amount, the current electrical quantity and preset reference value of AC system 1 are compared and are calculated, that is, can determine adjustment AC system 1
The out-of-limit scheme of electric current.In the present embodiment, it is adjusted the determination of scheme by station level control module 31, that is, utilizes outer circular current control
Unit processed and inner ring current control unit calculate current electrical quantity and preset reference value, are depicted as modulating wave, as adjust
Perfect square case, and the Adjusted Option is sent in valve grade control module 32.
The output end of valve grade control module 32 is connect with the input terminal of voltage source converter 4, and valve grade control module 32 is used
It is modulated in by modulating wave, obtains control instruction and voltage source converter 4 is controlled, is i.e. control voltage source converter
4 IGBT on-off.
Valve grade control module 32 is modulated processing to the Adjusted Option received, and generates control according to modulation result and refer to
It enables, voltage prototype inverter 4 is sent to, to control the alternating voltage and alternating current inside voltage source converter 4.
The DC side of voltage source converter 4 is connected with direct current system 5, is that voltage source converter 4 mentions by direct current system 5
For DC current and DC voltage, to carry out the change of current with AC system 1, the change of current operation of AC system and direct current system is realized,
The fault current for inhibiting AC system 1, guarantees the operation stability of electric system.
Inverter of the present embodiment in flexible DC transmission is voltage source converter, and maximum feature is to use
Turn-off device (usually IGBT) and high frequency modulated technology.
It is poor by the amplitude of adjusting inverter exit potential and the generator rotor angle between system voltage, it can independently control defeated
Active power and reactive power out.In this way, passing through the control to both ends converter station, so that it may realize between two AC networks
The mutual transmission of active power, at the same both ends converter station can with the separately adjustable respective reactive power for absorbing or issuing, from
And reactive power support is given to the AC system 1 joined.
To realize that the change of current with AC system 1 operates, in the present embodiment, voltage source converter 4 includes that several exchanges are changed
Galvanic electricity resists 41, six bridge arm change of current structure 42 of several three-phases and several DC capacitors 43；Six bridge arm change of current structure 42 of three-phase and direct current
System 5 connects, and each six bridge arm change of current structure 42 of three-phase is parallel-connection structure.
In the present embodiment, three six bridge arm change of current structures 42 of three-phase are parallel to direct current system 5, and six bridge arm of each three-phase changes
Flow structure 42 is symmetrical structure, i.e., is in both ends symmetrical structure with center.
Six bridge arm change of current structure 42 of three-phase includes several bridge arm reactance LarmWith several change of current submodule SM, along six bridge of three-phase
The middle part of arm change of current structure 42 to the position connecting with direct current system 5 is sequentially connected in series a bridge arm reactance LarmWith several change of current
Module SM.
One end of each exchange change of current reactance 41 is connected to the middle part of six bridge arm change of current structure 42 of three-phase, each exchange
The other end of change of current reactance 41 passes through a resistance R respectively and connect with AC system 1；Exchange the L of change of current reactance 41 as shown in figure 1s。
The junction of exchange change of current reactance 41 and six bridge arm change of current structure 42 of three-phase, DC capacitor is arranged in DC capacitor 43
43 quantity is identical as the quantity of six bridge arm change of current structure 42 of three-phase.Referring to Fig. 1, the first DC capacitor ucaWith outermost, ascend the throne
It sets a three-phase six bridge arm change of current structure 42 farthest apart from direct current system 5 to be connected, the second DC capacitor ucbWith apart from moderate
One six bridge arm change of current structure 42 of three-phase is connected, third DC capacitor uccThe nearest six bridge arm change of current structure of a three-phase with distance
42 are connected.
Current-limiting protection system provided in this embodiment, by the current electrical quantity of 2 real-time monitoring AC system 1 of measuring unit,
Judge that the i.e. electric current of the failure of AC system 1 is more prescribed a time limit, control methods are generated according to current electrical quantity by control system 3, with
The fault current for inhibiting AC system 1, i.e., be sent to voltage source converter 4 for the control instruction generated according to regulation and control scheme,
So that voltage source converter 4 adjusts the alternating voltage and alternating current of itself according to the control instruction, to go out with AC system 1
The alternating current of existing failure carries out change of current operation, guarantees the stability of DC current in the fault current of limiting AC system 1,
Guarantee the stability of voltage source converter 4, and then stablizes Operation of Electric Systems.
It referring to fig. 2, is the process of flexible direct current transmission converter station failure current limit guard method provided in an embodiment of the present invention
Figure, flexible direct current transmission converter station failure current limit as shown in Figure 1 protect system to execute, and this method comprises the following steps:
The current electrical quantity of S1, measuring unit real-time monitoring AC system, according to the current electrical quantity judgement exchange system
It is out-of-limit whether system electric current occurs；
In flexible direct current transmission converter station operation, easily there are the failures such as electric current is out-of-limit in AC system 1, therefore, in order to
The stable operation for guaranteeing electric system, needs to monitor in real time the state of AC system 1.
In the present embodiment, measuring unit is set in the power system, i.e., AC system 1 and voltage source converter 4 it
Between be arranged measuring unit 2, by measuring unit 2 monitor in real time AC system 1 data variation, be with accurate judgement AC system 1
It is no that electric current occur out-of-limit.
If it is out-of-limit that electric current occur in S2, the alternating current circuit, the current electrical quantity is sent to control system by measuring unit
System；
The current electrical quantity that measuring unit 2 monitors includes alternating current Is, alternating voltage Upcc, active-power P and idle
The numerical value after judging that electric current is out-of-limit according to above-mentioned numerical value, is delivered to control system 3 by measuring unit, by controlling by power Q
System 3 is timely controlled, and fault current is inhibited, and stablizes Operation of Electric Systems.
S3, the control system are according to the current electrical quantity switching control mode received, according to the control after switching
Mode processed generates current control instruction；And the current control instruction is sent to voltage source converter；
After control system 3 receives the current electrical quantity of AC system, processing calculating is carried out, to generate regulation and control scheme, into
Row accurately controls, and specific method is as follows:
Since control system 1 includes station level control module 31 and valve grade control module 32, control system 3 is carrying out
When being precisely controlled, need to carry out as steps described below:
S31, the station level control module control current electrical quantity and default electrical quantity and interior circular current in outer circular current
It is calculated in control, obtains target modulation wave, be delivered to valve grade control module；
Station level control module 31 receives the current electrical quantity for the AC system 1 that measuring unit 2 is sent, and controls mould using station level
Outer ring current control unit and inner ring current control unit in block 31 calculate current electrical quantity and default electrical quantity, defeated
Target modulation wave out, and be sent to valve grade control module 32 and be further processed.
S32, the valve grade control module are modulated processing to target modulation wave, according to modulation treatment result starting protection
Movement, is switched to active reactive control mode for control mode；And it according to the active reactive control mode, generates current
Control instruction.
Valve grade control module 32 demodulates target modulation wave, is regulated scheme, and according to the modulation treatment result
Starting protection movement, i.e., be switched to active reactive control mode for the control mode of current electric system, with limiting short-circuit current
Size.
After being switched to active reactive control mode, generates current control instruction and be sent to voltage source converter 4, to electricity
Potential source type inverter 4 is controlled.
S4, the voltage source converter inhibit the alternating current of AC system, realize exchange according to current control instruction
The change of current of system and direct current system operates.
Voltage source converter 4 is according to current control instruction, under active reactive control mode, controls alternating voltage and friendship
Galvanic electricity stream controls the active power and reactive power of point of common coupling.
When AC system 1 breaks down, inhibit alternating current to increase by inner ring current control, and then reaches inhibition and hand over
The purpose of the alternating current of streaming system 1.The electric current provided by the direct current system 5 that connect with voltage source converter 4, and exchanges
The electric current of system 1 carries out the change of current, so that the electric current of AC system 1 is restored normal, and then keep Operation of Electric Systems normal.
Specifically, as steps described below, the voltage source converter inhibits AC system according to current control instruction
Alternating current:
S41, according to the current control instruction, control loop integrator in the voltage source converter and reset；
After judging that AC system 1 breaks down, control mode is switched to active nothing by the protection act of control system 3
Function control mode carries out accurately change of current behaviour at this point, the loop integrator in control voltage source converter is reset again later
Make.
S42, according to the active reactive control mode, control the alternating voltage and alternating current in voltage source converter
Stream；
After resetting loop integrator, using active reactive control mode, according to default electrical quantity, to control voltage source
Alternating voltage and alternating current in type inverter are eliminated so that numerical value adjusted can be matched with AC system 1
The electric current of AC system 1 is out-of-limit.
S43, according to the alternating voltage and alternating current in the voltage source converter after control, adjust at point of common coupling
Current electrical quantity, inhibit the alternating current of AC system；Wherein, the current electrical quantity includes active power and idle function
Rate.
According to numerical value adjusted, under active reactive control mode, control amount be point of common coupling active power and
Reactive power, will be in alternating voltage adjusted and alternating current, with alternating voltage and the alternating current progress of point of common coupling
With to control the active power and reactive power of point of common coupling, and then inhibit the alternating current of AC system, eliminate electric current and get over
Limit.
In addition, in other embodiments, flexible direct current transmission converter station failure current limit guard method provided in this embodiment,
Further include:
S101, after completing primary current control process, the control system is by control mode by active reactive controlling party
Formula is restored to width phase control mode；
When AC system 1 breaks down, to be inhibited, control system 1 is switched control mode by width phase control mode
After active reactive control mode, after the one-stage control time, control system 1 is by control mode again by active reactive controlling party
Formula is switched to width phase control mode, and the initial value for controlling the loop integrator in voltage source converter at this time is assigned a value of ideal exchange
Voltage value.Wherein, voltage value when which can run for electric system normal table.
S102, the new current electrical quantity monitored according to the measuring unit judge the AC system with the presence or absence of electric current
It is out-of-limit；
After control mode is restored to width phase control mode, need to judge again current AC system whether there is also therefore
Therefore barrier also needs measuring unit monitoring AC system to be judged according to obtained new current electrical quantity.
If that there are electric currents is out-of-limit for S103, the AC system, cutting instruction is generated by the control system and being sent to electricity
Potential source type inverter, to cut off the connection of voltage source converter and AC system.
If it is out-of-limit that AC system still has electric current, by control system, cuts off voltage source converter and exchange and be
The connection of system；Out-of-limit if there is no electric current, then control system does not make any control instruction, and electric system continues to run.
From the above technical scheme, flexible direct current transmission converter station failure current limit provided in an embodiment of the present invention protection side
Method, by the current electrical quantity of measuring unit real-time monitoring AC system, when judging that AC system occurs according to current electrical quantity
Electric current is more prescribed a time limit, by control system according to current electrical quantity switching control mode, by voltage source converter according to control system
Instruction carry out AC and DC the change of current operation, realize to voltage source converter exchange side electric voltage frequency control, in turn
Achieve the purpose that inhibit AC system electric current out-of-limit.As it can be seen that method provided in this embodiment, it can be when realizing fault in ac transmission system
Fault current limiting, while the damage to voltage source converter can be reduced, improve the operation stability of electric system.
Illustrate flexible direct current transmission converter station failure provided in an embodiment of the present invention limit With reference to embodiment
The beneficial effect that stream guard method and system can obtain.
Fig. 3 is the schematic diagram of flexible direct current transmission converter station failure current limit protection system when breaking down；Fig. 4 (a) (b)
(c) (d) (e) is the Dynamic Simulation Results figure of flexible direct current transmission converter station failure current limit protection system when breaking down.
Referring to Fig. 3 and Fig. 4 (a) (b) (c) (d) (e), with passive network through seven power level voltage source type inverter grid-connected systems
For, alternating voltage 220kV, DC voltage 500kV, submodule capacitor are 1000uF.AC three-phase occurs in 2s
Short trouble, failure continue 0.1s, and current reference direction is rectification direction.PSCAD emulation is carried out according to model, obtains voltage source
The dynamic characteristic of switching control mode and non-switching control mode compares type inverter after a failure.
(a) (b) (c) (d) (e) referring to fig. 4, in figure: Udc- DC voltage of the invention is not used；Udcnew- using this
The DC voltage of invention；Isa- a phase alternating current of the invention is not used；Isanew- use a phase alternating current of the invention；
Upcc- alternating voltage of the invention is not used；Upccnew- use alternating voltage of the invention；Ps- friendship of the invention is not used
Flow active power；Psnew- exchange active power of the invention is not used；Qs- exchange reactive power of the invention is not used；
Qsnew- exchange reactive power of the invention is not used.
After breaking down in 2s, the alternating current amplitude of voltage source converter is promoted to 40kA, alternating voltage from 2kA
It is down to 0 from 220kV, active power is down to 0 from -600MW, and reactive power rises to -800MVar by -30MVar.Control system exists
2.005s monitors that failure, change control mode are active reactive control mode, and alternating current is suppressed to 2kA at this time,
Voltage source converter still works in normal operating condition.Failure vanishes when 2.1s, system restore normal, and control system is in 2.3s
After switch back into width phase control mode, DC voltage fluctuation is between 480kV to 550kV in whole process.
As it can be seen that voltage source converter after AC system breaks down still in normal operating conditions, DC voltage compared with
For stabilization, alternating current is limited within 2kA, improves the stability of flexible direct current transmission converter station, raising and flexible direct current
The stability of the connected electric system of power transmission converter station.
Those skilled in the art after considering the specification and implementing the invention disclosed here, will readily occur to of the invention its
Its embodiment.This application is intended to cover any variations, uses, or adaptations of the invention, these modifications, purposes or
Person's adaptive change follows general principle of the invention and including the undocumented common knowledge in the art of the present invention
Or conventional techniques.The description and examples are only to be considered as illustrative, and true scope and spirit of the invention are by appended
Claim is pointed out.
It should be understood that the present invention is not limited to the precise structure already described above and shown in the accompanying drawings, and
And various modifications and changes may be made without departing from the scope thereof.The scope of the present invention is limited only by the attached claims.
Claims (10)
1. a kind of flexible direct current transmission converter station failure current limit protects system characterized by comprising AC system, voltage source
Type inverter, control system and measuring unit；Wherein,
The AC system is connected by alternating current circuit with the side that exchanges of the voltage source converter；
The measuring unit is arranged at the point of common coupling that AC system is connected with voltage source converter, measuring unit it is defeated
The connection of the input terminal of outlet and control system；Measuring unit is used to monitor the current electrical quantity of AC system, and, it will monitor
Current electrical quantity be delivered to control system；
The input terminal of the output end of the control system and voltage source converter connects, and the control system is used for receiving
The current electrical quantity handled, the voltage source converter is delivered to after processing, controls the voltage-source type change of current
Alternating voltage and alternating current inside device；
The DC side of the voltage source converter is connected with direct current system, realizes the change of current behaviour of AC system and direct current system
Make.
2. system according to claim 1, which is characterized in that the voltage source converter includes several exchange change of current electricity
Anti-, several six bridge arm change of current structures of three-phase and several DC capacitors；The six bridge arm change of current structure of three-phase is connect with direct current system,
Each six bridge arm change of current structure of three-phase is parallel-connection structure；
One end of each exchange change of current reactance is connected to the middle part of six bridge arm change of current structure of three-phase, each exchange
The other end of change of current reactance passes through a resistance respectively and connect with AC system；
The junction of exchange change of current reactance and six bridge arm change of current structure of three-phase is arranged in the DC capacitor.
3. system according to claim 2, which is characterized in that the six bridge arm change of current structure of three-phase is symmetrical structure；Three
Six bridge arm change of current structure of phase includes several bridge arm reactance and several change of current submodules, extremely along the middle part of six bridge arm change of current structure of three-phase
The position connecting with direct current system is sequentially connected in series a bridge arm reactance and several change of current submodules.
4. system according to claim 1, which is characterized in that the control system includes station level control module and valve grade control
Molding block, the input terminal of the station level control module and the output end of measuring unit connect, for what is monitored to measuring unit
Current electrical quantity is handled, and is obtained modulating wave, is delivered to valve grade control module；
The output end of the valve grade control module and the input terminal of voltage source converter connect, and valve grade control module will be for that will adjust
Wave processed is modulated, and is obtained control instruction and is controlled voltage source converter.
5. system according to claim 4, which is characterized in that the station level control module includes outer ring current control unit
With inner ring current control unit；The outer ring current control unit and inner ring current control unit are for current electrical quantity and in advance
If reference value is calculated, obtains modulating wave and be delivered to valve grade control module.
6. system according to claim 1, which is characterized in that the AC system includes passive network, wind-powered electricity generation energy net
Network or photovoltaic energy network.
7. a kind of flexible direct current transmission converter station failure current limit guard method, which is characterized in that the described method includes:
The current electrical quantity of measuring unit real-time monitoring AC system judges whether AC system goes out according to the current electrical quantity
Existing electric current is out-of-limit；
If it is out-of-limit that electric current occurs in the alternating current circuit, the current electrical quantity is sent to control system by measuring unit；
The control system is raw according to the control mode after switching according to the current electrical quantity switching control mode received
At current control instruction；And the current control instruction is sent to voltage source converter；
The voltage source converter inhibits the alternating current of AC system according to current control instruction, realize AC system and
The change of current of direct current system operates.
8. the method according to the description of claim 7 is characterized in that the control system includes station level control module and valve grade control
Molding block；And control system is according to the current electrical quantity switching control mode received as steps described below, after switching
The control mode generate current control instruction:
The station level control module by current electrical quantity and default electrical quantity outer circular current control and inner ring current control in into
Row calculates, and obtains target modulation wave, is delivered to valve grade control module；
The valve grade control module is modulated processing to target modulation wave, is acted according to modulation treatment result starting protection, will
Control mode is switched to active reactive control mode；And it according to the active reactive control mode, generates current control and refers to
It enables.
9. the method according to the description of claim 7 is characterized in that the voltage source converter is according to working as steps described below
Preceding control instruction inhibits the alternating current of AC system:
According to the current control instruction, the loop integrator controlled in the voltage source converter is reset；
According to the active reactive control mode, alternating voltage and alternating current in voltage source converter are controlled；
According to the alternating voltage and alternating current in the voltage source converter after control, the current electricity at point of common coupling is adjusted
Tolerance inhibits the alternating current of AC system；Wherein, the current electrical quantity includes active power and reactive power.
10. the method according to the description of claim 7 is characterized in that further include:
After completing primary current control process, the control system is restored control mode to width by active reactive control mode
Phase control mode；
According to the new current electrical quantity that the measuring unit monitors, judge that the AC system is out-of-limit with the presence or absence of electric current；
If that there are electric currents is out-of-limit for the AC system, cutting instruction is generated by the control system and being sent to the voltage-source type change of current
Device, to cut off the connection of voltage source converter and AC system.
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