CN106505641B - The AC/DC decoupling control method of modularization multi-level converter and its application - Google Patents
The AC/DC decoupling control method of modularization multi-level converter and its application Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a kind of AC/DC decoupling control methods of modularization multi-level converter, it is included in current inner loop control and increases DC current control, making current inner loop control includes AC current control and DC current control, to make the output of output and the DC current control of AC current control collectively as the main component of the output voltage reference value of each phase bridge arm of modularization multi-level converter；The reference value of AC current control and DC current control is controlled respectively, while controlling the output of AC current control and DC current control, the control to main component can be realized, and then can realize that inverter is latched because of bridge arm overcurrent when preventing DC Line Fault.The application that the invention also discloses the above methods in flexible HVDC transmission system.Alternating current, DC current and the submodule capacitor voltage of each converter station are controlled in safe range, it can be achieved that the DC Line Fault of flexible HVDC transmission system passes through.
Description
Technical field
The invention belongs to electric system transmission & distribution electro-technical fields, more particularly, to a kind of modularization multi-level converter
AC/DC decoupling control method and its application in aerial DC transmission system.
Background technique
Modularization multi-level converter (Modular Multilevel Converter, MMC) technology has construction module
Change, be easy to the advantages that extending, since proposition, has been widely used in industry.By the end of currently, all throwings in the world
The MMC high voltage direct current transmission project of fortune be using based on half-bridge submodule semi-bridge type MMC technology or with half-bridge submodule
Two level of cascade (Cascaded two level, CTL) technology of (Half bridge sub-module, HBSM) homotype.But
Semi-bridge type MMC and CTL there are problems that DC Line Fault cannot be coped with.After DC Line Fault occurs for transmission line of electricity, AC system
Fault current persistently will be provided to fault point by the freewheeling diode of semi-bridge type MMC and CTL, it usually needs inverter is coupled
AC circuit breaker to cutting off direct fault current.Therefore, existing engineering mostly uses direct current cables to transmit electricity greatly to reduce
The probability that DC Line Fault occurs.
With the further development of HVDC Transmission Technology, voltage, the capacitance grade of flexible HVDC transmission system are higher and higher,
Transmission range is more and more remoter, this, which to transmit at a distance using overhead line, becomes inexorable trend.Direct current overhead transmission line failure rate compared with
Height, and be mostly transient fault, the method for cutting off direct fault current using AC circuit breaker is cut-off will substantially increase
The time of system break power supply and the time to restore electricity, jeopardize the safe and stable operation of electric system and because interruption of power supply can
It can cause heavy economic losses and social concern.
In order to cope with DC Line Fault problem, a kind of effective method is using semi-bridge type submodule and bridge-type submodule string
Mixed type MMC made of connection.Occur DC Line Fault when, by be latched mixed type MMC power electronic devices driving signal to
Direct fault current is blocked, prevents from cut-offfing AC circuit breaker.The method of above-mentioned locking requires mixed type MMC to interrupt, and
After DC Line Fault blocking, need to restart mixed type MMC, Fault Isolation time and the time that restores electricity are still longer.
In order to overcome the above problem, prevent from being latched mixed type MMC, patent document CN104300569A during DC Line Fault
Disclose the DC Line Fault traversing control method of mixed type MMC a kind of, it is characterised in that when DC Line Fault occurs, real-time monitoring is straight
Side residual voltage value is flowed, according to the alternating voltage reference value of DC voltage residual voltage value and output required for the every phase of MMC, is calculated
It obtains in every phase, the reference voltage value of upper and lower bridge arm full-bridge submodule equivalent voltage source and half-bridge submodule equivalent voltage source.
Academic paper " submodule mixed type MMC-HVDC DC Line Fault passes through control strategy " that Kong Ming et al. is delivered (Kong Ming, Tang Guangfu,
The deep pool submodule mixed type MMC-HVDC DC Line Fault of he passes through control strategy [J] Proceedings of the CSEE, and 2014,34
(30): 5343-5351 the DC Line Fault that a kind of mixed type MMC is proposed in) passes through control strategy, during DC Line Fault,
By the DC component zero setting of bridge arm output voltage reference value, bridge arm output voltage is all generated by full-bridge submodule, half-bridge submodule
The number zero setting of block investment.
Scheme in CN104300569A needs to correct the ginseng of each bridge arm using the DC side residual voltage value monitored
Voltage value is examined, is substantially a kind of open loop control strategy.The scheme of Kong Ming et al. and the scheme of CN104300569 have it is similar it
Place, difference are not real-time monitoring DC side residual voltage value, but artificially setting DC side residual voltage value is zero, this two
The defect of class method is that closed-loop control can not be formed to DC current and submodule capacitor voltage, to there is generation overcurrent
Or the security risk of submodule capacitance overvoltage, actually by Figure 12 of above-mentioned paper it is found that during DC Line Fault, DC current
Value rises to instant of failure 8kA or so by the 1.6kA of stable state, and direct current overcurrent multiple is up to 5 times, may burn MMC.
Summary of the invention
Aiming at the above defects or improvement requirements of the prior art, the present invention provides a kind of aerial flexible HVDC transmission systems
AC/DC decoupling control method controls framework by redesigning existing MMC, so that normal operation and DC Line Fault phase
Between, the alternating current of each converter station of flexible HVDC transmission system is maked somebody a mere figurehead, DC current and submodule capacitor voltage are controlled
System in safe range, realizes that the DC Line Fault of aerial flexible HVDC transmission system passes through.
A kind of AC/DC decoupling control method of modularization multi-level converter, has output for realizing part submodule
Uninterrupted operation of the modularization multi-level converter of negative voltage ability under AC fault and/or DC Line Fault, feature exist
In the control method includes
Increase DC current control in current inner loop control, so that the current inner loop control includes AC current control
It is controlled with DC current, to may make the output of output and the DC current control of the AC current control collectively as institute
State the main component of the output voltage reference value of each phase bridge arm of modularization multi-level converter；
The reference value of the AC current control and DC current control is controlled respectively, while controlling the alternating current flow control
The output of system and DC current control, can be realized the control to the main component, and then can realize when preventing DC Line Fault
Inverter is latched because of bridge arm overcurrent.
As present invention further optimization, the reference value of the AC current control includes exchange watt current reference value
With exchange two components of reactive current reference value, wherein be set as the output of MMC energy hole for watt current reference value is exchanged,
Wherein the MMC energy hole is used to control the physical quantity for characterizing MMC institute storage energy to corresponding reference value.
As present invention further optimization, the reference value of the DC current control is arranged to direct current outer loop control
Output, wherein the direct current outer loop control is for controlling amount relevant to dc power, the preferably direct current of dc power or MMC
Port voltage.
It further include that additional DC current ginseng is superimposed in the output of direct current outer loop control as present invention further optimization
Value is examined, wherein the additional DC current reference value is positive value when submodule average capacitor voltage is higher than capacitance voltage upper limit value,
When submodule average capacitor voltage is lower than capacitance voltage lower limit value, the additional DC current reference value is a negative value；Wherein, whole
Flow the positive direction that direction is alternating current, MMC is the positive direction of DC current to DC line Injection Current.
As present invention further optimization, the additional DC current reference value is defeated by upper clipping ring and lower clipping ring
It is formed by stacking out, wherein the input of the upper limit width ring is the difference of submodule average capacitor voltage and the capacitance voltage upper limit, it should
Difference obtains the output of the upper clipping ring after proportional, integral device；The input of the lower clipping ring is submodule average capacitance
The difference of voltage and capacitance voltage lower limit, the difference obtain the output of the lower clipping ring after proportional, integral device；Wherein, institute
The upper limit for stating the integrator of clipping ring is set as a positive value, and lower limit is set as zero；The upper limit of the integrator of the lower clipping ring
It is set as zero, lower limit is set as a negative value.
As present invention further optimization, the reference value of the DC current control is arranged to MMC energy hole
Output, wherein the MMC energy hole is used to control the physical quantity for characterizing MMC institute storage energy to corresponding reference value.
As present invention further optimization, the exchange watt current reference value is arranged to exchange active outer loop control
Output, the active outer loop control of the exchange is used for for controlling amount relevant to active power, preferably exchange active power,
Frequency, dc power, MMC DC port voltage.
It further include being superimposed to add active electricity in the output for exchanging active outer loop control as present invention further optimization
Reference value is flowed, wherein the additional DC current reference value is one when submodule average capacitor voltage is higher than capacitance voltage upper limit value
Negative value, when submodule average capacitor voltage is lower than capacitance voltage lower limit value, the additional DC current reference value is a positive value；Its
Middle rectification direction is the positive direction of alternating current, and MMC is the positive direction of DC current to DC line Injection Current.
It is described to add active current reference value by the defeated of upper clipping ring and lower clipping ring as present invention further optimization
It is formed by stacking out, wherein the input of the upper limit width ring is the difference of capacitance voltage upper limit value and submodule average capacitor voltage,
The difference obtains the output of " upper clipping ring " after proportional, integral device, the input of the lower clipping ring be capacitance voltage lower limit with
The difference of submodule average capacitor voltage, the difference obtain the output of " lower clipping ring " after proportional, integral device；On wherein described
The upper limit of the integrator of clipping ring is set as zero, and lower limit is set as negative value, and the upper limit setting of the integrator of " lower clipping ring " is positive
Value, lower limit are set as zero.
It is described to control the physical quantity for characterizing MMC institute storage energy to corresponding ginseng as present invention further optimization
Examining value includes but is not limited to control the energy storage summation of all submodule capacitors of MMC to corresponding reference value, by all submodules of MMC
The average capacitor voltage of block is controlled to be controlled to reference value, by the energy storage summation of the submodule capacitor of all exportable negative levels of MMC
Extremely corresponding reference value, and the average capacitor voltages of all submodules for having output negative level ability of MMC are controlled to right
The reference value answered.
As present invention further optimization, the output of the AC current control is the reference of MMC ac output voltage
Value, the output of the DC current control are the half of the reference value of MMC DC output voltage.
As present invention further optimization, the main component of bridge arm output voltage reference value (comes from electric current in each phase
The component of inner loop control) be DC current control output and AC current control output difference, each phase lower bridge arm is defeated
The main component of voltage reference value is the sum of output and output of AC current control of DC current control out.
As present invention further optimization, when DC Line Fault occurs, the output that the DC current is controlled is quick
Reduce the control realized to the main component, and then realizing prevents inverter when DC Line Fault to be latched because of bridge arm overcurrent.
As present invention further optimization, DC current control output is quickly reduced by by above-mentioned direct current
Integrator in flow control resets or sets a lower limit value for its initial value, so that integrator is in zero initial value or negative initial value
On restart to integrate, to realize the output for quickly reducing DC current control.
It is when DC Line Fault occurs, the exchange watt current reference value is quick as present invention further optimization
Change near zero setting, and then realizes that reducing exchange side gives modularization multi-level converter charge/discharge, prevents modular multilevel from changing
Stream device generation sustained overvoltage/under-voltage.
As present invention further optimization, the quick change exchange watt current reference value zero setting is nearby preferably
The integrator of MMC energy hole is reset, so that integrator restarts to integrate on zero initial value.
As present invention further optimization, each bridge arm output voltage reference value also includes loop current suppression controller output ginseng
Examine the negated amount of voltage.
As present invention further optimization, can also the DC current control output on superposition actual measurement obtain change
The DC voltage value for flowing device direct current output port, to improve response speed.
As present invention further optimization, when can also limit DC Line Fault generation by increasing the inductance of MMC DC side
Carve the incrementss that MMC DC current in the period is started working to DC current controller.
It is another aspect of this invention to provide that the AC/DC decoupling control method for providing a kind of modularization multi-level converter exists
Both ends or multiterminal make somebody a mere figurehead the application in flexible HVDC transmission system, wherein the both ends or multiterminal make somebody a mere figurehead flexible DC transmission system
The converter station of system includes the MMC that part submodule has output negative voltage ability, and the part submodule has output negative voltage
The MMC of ability is all made of the control method and is controlled.
It is another aspect of this invention to provide that the AC/DC decoupling control method for providing a kind of modularization multi-level converter exists
Make somebody a mere figurehead the application in flexible HVDC transmission system in both ends, wherein make somebody a mere figurehead the change of current at the every end of flexible HVDC transmission system in the both ends
Stand the MMC for having output negative voltage ability including part submodule, and specifying the converter station of either end is DC voltage control
It stands and other end converter station is power control station, and the part submodule in two converter stations has output negative voltage ability
MMC is all made of the control method and is controlled, to pass through the reference for the DC voltage control for reducing DC voltage control station
Value is to realize the DC operating voltage for reducing the both ends and making somebody a mere figurehead flexible HVDC transmission system.
It is another aspect of this invention to provide that the AC/DC decoupling control method for providing a kind of modularization multi-level converter exists
Application in flexible HVDC transmission system comprising when monitoring that DC Line Fault occurs, ginseng that the DC current is controlled
It examines value to be directly disposed as absorbing DC current from AC line trackside, to quickly extinguish fault electric arc.
As present invention further optimization, the AC line trackside absorbs -0.1 that DC current is rated direct current
~-0.3 times.
It is another aspect of this invention to provide that the AC/DC decoupling control method for providing a kind of modularization multi-level converter exists
Application in flexible HVDC transmission system, during restoring electricity, by either one or two of entire flexible HVDC transmission system or more
The reference value of the DC current control of a MMC is set as lesser positive value, direct current outer loop control is replaced, if after a period of time
DC voltage is increased over certain value, then judges that DC Line Fault has been removed, and will then enable the outer ring controller of each converter station,
The method for realizing the fast recovery of power supply of flexible HVDC transmission system.
It is another aspect of this invention to provide that providing a kind of MMC degeneration that part submodule is had to output negative voltage ability
For the operation method of semi-bridge type MMC, which is characterized in that the part submodule has the MMC of output negative voltage ability using institute
The control method stated is controlled, wherein it is rated direct voltage that the output of DC current control is maintained when operating normally, and
DC current control is carried out when DC Line Fault.
In general, control method of the invention is compared and the prior art, is had the following technical effect that
(1) the AC/DC decoupling control method invented includes that AC current control and DC current control in two electric currents altogether
Ring control, two current inner loop controls ensure that alternating current and DC current are in closed-loop control under any operating condition
State avoids power electronic devices straight so that it is guaranteed that overcurrent does not occur for the semiconductor devices of converter station during DC Line Fault
It is damaged during stream failure because of overcurrent；
(2) for the solution of the present invention in normal operation and DC Line Fault, control logic is consistent, without using the direct current of actual measurement
The fault-signal that voltage residual value or monitoring obtain, and the reference value of bridge arm output voltage is changed to correspond under malfunction
Value, i.e., it is not necessary that controller switched to the controller under malfunction from the controller under normal operating conditions so that
It controls simple and reliable.
(3) the solution of the present invention applies also for the aerial flexible HVDC transmission system in both ends and the aerial flexible direct current of multiterminal is defeated
In electric system, put out suitable for making somebody a mere figurehead the control under the conventional control of flexible HVDC transmission system, DC Line Fault state, and actively
Arc quickly restarts, reduces DC voltage operation, makes somebody a mere figurehead soft straight system degradation as the control of the operation of conventional half bridge MMC etc..
Detailed description of the invention
Fig. 1 is a kind of typical bridge-type modularization multi-level converter topology in the prior art；
Fig. 2 is a kind of typical intersection cascade connection type modularization multi-level converter topology in the prior art；
Fig. 3 is the mixed type MMC topology being made of bridge-type submodule semi-bridge type submodule；
Fig. 4 is the mixed type MMC topology being made of intersection cascade connection type submodule semi-bridge type submodule；
Fig. 5 is that existing modularization multi-level converter typical case controls topology；
Fig. 6 is the alternating current-direct current using exchange watt current control submodule average capacitor voltage of one embodiment of the invention
Decoupling control principle assumption diagram；
Fig. 7 is the direct current decoupling control principle structure chart of another embodiment of the present invention；
Fig. 8 is the alternating current-direct current solution using DC current control submodule average capacitor voltage of another embodiment of the invention
Coupling control principle structure chart；
Fig. 9 is the AC/DC decoupling control principle structure chart of further embodiment of the present invention；
Figure 10 is the two-terminal direct current transmission system schematic diagram being made of half-bridge full-bridge mixed type MMC；
Figure 11 is the instantaneity DC Line Fault simulation result diagram to the AC/DC decoupling control method of the embodiment of the present invention；
Figure 12 is the permanent DC Line Fault simulation result diagram to the AC/DC decoupling control method of the embodiment of the present invention.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
Not constituting a conflict with each other can be combined with each other.
FIG. 1 to FIG. 4 is typically to be applicable to the MMC topology of control method proposed by the invention in the prior art.Such as
Shown in Fig. 1~4, wherein Fig. 1 is bridge-type MMC, and each bridge arm is connected in series by multiple full-bridge submodules.Fig. 2 is by intersecting
The MMC topology that cascade connection type submodule is constituted, each bridge arm of Fig. 2 are connected in series by multiple intersection cascade connection type submodules.Fig. 3 serves as reasons
The mixed type MMC topology that full-bridge submodule and half-bridge submodule are constituted, each of which bridge arm by multiple half-bridge submodules with it is multiple
Full-bridge submodule is connected in series.Fig. 4 is the mixed type MMC topology being made of intersection cascade connection type submodule and half-bridge submodule,
Each bridge arm is connected in series by multiple half-bridge submodules and multiple cascade submodules that intersect.Its topological common trait of above-mentioned MMC
It is that each bridge arm contains the submodule (such as full-bridge submodule and intersection cascade connection type submodule) of exportable negative voltage, this hair
Bright control method is suitable for various bridge arms and has the MMC topology for exporting lasting negative voltage ability.Bridge arm has output and persistently bears
The MMC of voltage capability is generally used for aerial flexible HVDC transmission system, but it is of the invention the control method is not limited to this, such as together
Sample is suitable for the flexible HVDC transmission system using direct current cables or direct current cables and direct current overhead line mixed connection route.
Each primary variables or the physical significance of abbreviation involved in various embodiments of the present invention are listed in the table below in 1.
Each primary variables involved in 1 embodiment of the present invention of table, abbreviation physical significance
Fig. 5 is the Typical Controller of existing module multilevel converter, mainly by active outer loop control, idle outer ring control
System, AC current control, the change of current inhibit control to constitute, and the DC component of bridge arm output voltage reference value is fixed as nominal DC
The half of voltage switches to other open loop values in failure, causes a problem in that, can not effectively control during DC Line Fault
Direct fault current.
Fig. 6 is control principle drawing corresponding to the control method of one embodiment of the invention, as shown in fig. 6, the embodiment
HVDC Modulation ratio Mdc is introduced in control method, and HVDC Modulation is obtained into the defeated of MMC than being multiplied with rated direct voltage Vdcn
Direct voltage reference value out.It only include d axis modulation ratio Md and q axis modulation ratio Mq existing MMC controller (such as Fig. 5), and
The control method of the present embodiment increases a control freedom degree, so that aerial in addition to further comprising Mdc comprising Md, Mq
Flexible HVDC transmission system can control exchange watt current Id simultaneously, exchange reactive current Iq and DC current Idc.And it is existing
MMC controller current inner loop control level only include AC current control (i.e. can only control exchange watt current with exchange nothing
Function electric current).
According to MMC basic theories, when bridge arm circulation is adequately suppressed, the expression formula of bridge arm current is iarm=idc/3+
Iac/2, wherein iarm, idc, iac respectively represent bridge arm current, DC current and each phase alternating current of MMC.When bridge arm electricity
High (such as twice more than bridge arm current rated peak) is flowed through, MMC will be latched because of bridge arm overcurrent.Existing control method
It may insure that MMC does not occur to exchange overcurrent, but due to not having to control the circuit of DC current, be unable to ensure and direct current mistake does not occur
Electric current.And the control method that the present embodiment is proposed can control alternating current and DC current simultaneously, so that it is guaranteed that any operating condition
Under, overcurrent does not occur for the bridge arm of MMC.
The principle of modulation ratio Mdc control DC current is through the output DC voltage using closed loop feedback control MMC
To accurately control DC current.In order to enable Mdc can accurately control DC current, the submodule capacitor voltage of MMC needs
It remains constant, MMC energy hole (such as submodule average capacitor voltage control of Fig. 6), benefit is devised in this embodiment scheme
With exchange watt current by MMC energy hole in reference value.It is alternating current that rectification direction is preferably set in various embodiments of the present invention
The positive direction of stream, MMC to DC line Injection Current be DC current positive direction.Submodule average capacitor voltage can pass through
It is obtained to total divided by submodule again after the capacitance voltage summation of all submodules.General only investment can export during DC Line Fault
The submodule of negative voltage, therefore to improve the response speed of MMC energy hole, submodule average capacitor voltage can also be by all tools
The sum of the submodule capacitor voltage of standby output negative voltage ability is obtained divided by the submodule sum for having output negative voltage ability.?
Under normal operating condition, the submodule capacitor voltage Pressure and Control algorithm of MMC will maintain the capacitance voltage of all submodules automatically
Near the reference value of submodule capacitor voltage average value.
As shown in fig. 6, the output of " DC current control " part is the reference value that MMC exports DC voltage in the present embodiment
0.5 times, the output of " AC current control " part is the reference value of MMC output AC voltage.Bridge arm output voltage in each phase
0.5 times of reference value that reference value is taken as MMC output DC voltage subtracts MMC output AC voltage reference value, each phase lower bridge arm
Output voltage reference value is taken as 0.5 times of reference value of MMC output DC voltage and MMC output AC voltage reference value.Pass through
" modulation and Pressure and Control " can be realized so that each bridge arm of MMC exports corresponding bridge arm output voltage reference value to alternating current
With the accurate control of DC current.
Fig. 6 remaining " idle outer loop control ", " direct current outer loop control ", " loop current suppression control ", " modulation with it is voltage-controlled
System " is well-known technique, and technical detail does not repeat.Since the control method of the present embodiment can make the exchange of MMC export
The decoupling of the DC output voltage of voltage and MMC, is referred to as AC/DC decoupling control method.
It in a preferred embodiment,, can be by DC current after monitoring DC Line Fault in order to reduce direct fault current
The integrator of inner loop control is reset, or is set as the lower limit of HVDC Modulation ratio, so that integrator is opened under new initial value
Begin integral, reduces HVDC Modulation ratio.
In a preferred embodiment, it for the charge and discharge of submodule capacitor voltage during reducing DC Line Fault, can monitor
To after DC Line Fault, the integrator of MMC energy controller is reset, thus reduce the absolute value of exchange watt current reference value,
Reduce exchange side to the charge/discharge effect of MMC submodule capacitor.
In a preferred embodiment, because there are certain operating lags for DC current control, in order to be controlled in DC current
Direct fault current is limited before effect, can suitably increase the direct current current-limiting inductance of MMC.
In embodiment shown in fig. 6, when AC system breaks down, it is understood that there may be exchange watt current is unable to control son
The hidden danger of module average capacitor voltage, another embodiment shown in Fig. 7 proposes the direct current outer loop control of above-described embodiment thus
Further improved technical solution is gone out.As shown in fig. 7, the embodiment principle is, folded in the output of direct current outer loop control
Additional DC current reference value Δ Iref is added.When submodule average capacitor voltage is higher than submodule capacitor voltage upper limit valueWhen, " direct current outer ring additional control " will export a positive Δ Iref to increase what DC line was absorbed from MMC
Energy.When submodule average capacitor voltage is lower than submodule capacitor voltage lower limit valueWhen, " direct current outer ring additional control "
By a negative Δ Iref is exported to reduce the energy that DC line is absorbed from MMC.
It adds DC current reference value described in Fig. 7 to be formed by stacking by the output of upper clipping ring and lower clipping ring, wherein described
The input of upper clipping ring is the difference of submodule average capacitor voltage and the capacitance voltage upper limit, and the difference is after proportional, integral device
Obtain the output of the upper clipping ring；The input of the lower clipping ring is submodule average capacitor voltage and capacitance voltage lower limit
Difference, the difference obtain the output of the lower clipping ring after proportional, integral device, and the upper limit of the integrator of the upper clipping ring is set
It is set to a positive value, lower limit is set as zero；The upper limit of the integrator of the lower clipping ring is set as zero, and lower limit is set as a negative value,
In this way, the integrator output of upper clipping ring and lower clipping ring and total output are restricted to saturation value when operating normally
Zero, upper clipping ring and lower clipping do not work；When submodule average capacitor voltage exceeds upper and lower limit, upper clipping ring and lower clipping
Ring exits saturation state, adjusts DC current reference value to maintain submodule average capacitor voltage within the scope of upper and lower limit.
Fig. 8 is the control method of another embodiment of the present invention, current inner loop control and embodiment illustrated in fig. 6 complete one
It causes, difference is the producing method of the embodiment shown in Fig. 8 exchange watt current reference value and DC current reference value not phase
Together.Embodiment illustrated in fig. 6 be using exchange watt current control submodule average capacitor voltage, using DC current control with
The relevant amount of MMC active power (such as DC voltage or dc power), and the present embodiment shown in Fig. 8 is then active using exchanging
Current control amount relevant to MMC active power, utilizes DC current control submodule average capacitor voltage.Shown in Fig. 8
Embodiment is compared to the advantage of embodiment illustrated in fig. 6, " DC current control " is disabled and when to maintain Mdc be 1, Fig. 8 institute
The present embodiment shown is degenerated for conventional MMC control.So " DC current control " can be disabled operating normally, only monitoring
It to after DC Line Fault, enables " DC current control ", to simplify the control mode of aerial flexible HVDC transmission system.
When DC Line Fault occurs, even if DC current is controlled in safe range, submodule capacitor voltage may be located
In uncontrolled state, for this purpose, another embodiment shown in Fig. 9 gives to the improved of the active outer ring of embodiment illustrated in fig. 8
Technical solution.The principle of the present embodiment is that output one is positive when submodule average capacitor voltage is lower than lower limit value is attached with
Function current-order is superimposed upon in the output of " active outer loop control ", and submodule average capacitor voltage exports one when being higher than lower limit value
The negative active current-order that adds is superimposed upon in the output of " active outer loop control ".
Figure 10 is the validity for controller designed by the emulation testing present invention.MMC1, MMC2's is specified in Figure 10
DC voltage and rated power are each bridge arm of ± 320kV and 1000MW, MMC1 and MMC2 by 100 full-bridge submodules
It is connected in series with 100 half-bridge submodules, the voltage rating of each submodule is taken as 3.2kV, the submodule of each submodule
Capacitor is 5mF.When normal operation, MMC1 is used to control the DC port voltage of MMC1, and MMC2 is used to control MMC2 transmission
Active power.
Figure 11 is instantaneity DC Line Fault simulation result diagram, and anode occurs for direct-current overhead power transmission line straight to cathode when 1.0s
Failure is flowed, when 1.1s, DC Line Fault is removed automatically.Figure 11 (a) is the direct voltage reference value and measured value of MMC1, it is known that direct current
During failure, DC voltage falls to zero or so, after fault clearance, and DC voltage quickly recovers to reference value.
Figure 11 (b) is submodule capacitor voltage average value.It is found that under non-faulting state, submodule capacitor voltage average value
It is controlled near reference value, DC Line Fault only brings 10% or so disturbance to submodule capacitor voltage.
Figure 11 (c) is DC current reference value and measured value.It knows under non-faulting state, DC current is controlled to direct current
Current reference value, during DC Line Fault, DC current only rises to 2 times of rated value, and serious direct current overcurrent does not occur.
Figure 11 (d) and (e) be d axis AC electric current and q axis AC electric current reference value and measured value.It is found that alternating current
Corresponding reference value is controlled to during operating normally with DC Line Fault.
The upper bridge arm current and lower bridge arm electric current that Figure 11 (f) and (g) are MMC1.Due to DC current and alternating current quilt
It is strict controlled near respective reference value, therefore the bridge arm of MMC is almost not subject to overcurrent.
Figure 11 (h) is the capacitance voltage of the 1st~32 work song module of bridge arm in the A phase of MMC1, it is known that, when normal operation, son
Module capacitance voltage reaches good equilibrium, and during DC Line Fault, the peak of submodule capacitor voltage is only risen to from 3.6kV
4kV.Submodule capacitance overvoltage will not occur during DC Line Fault for controller designed by the invention.
Figure 12 is permanent DC Line Fault simulation result.When 1.0s, makes somebody a mere figurehead DC power transmission line and occur permanently extremely to pole
DC Line Fault, when 1.2s, the referenced reactive current of MMC1 is from 0 step to 0.5pu.The DC voltage that Figure 12 (a) is MMC1 refers to
Value and measured value, during Figure 12 (a) shows DC Line Fault, the DC voltage of MMC1 drops to 0.Figure 12 (b) is the active of MMC1
Power and reactive power waveform, by the waveform after 1.2s it is found that during DC Line Fault, MMC still can export nothing to AC system
Function power.Figure 12 (c)-(d) is the upper bridge arm current and lower bridge arm electric current of MMC1, it is known that after permanent DC Line Fault occurs, MMC
Bridge arm be also not subject to overcurrent.Figure 12 (e) is the capacitance voltage waveform of the 1st~32 work song module of bridge arm in the A phase of MMC1, can
Know, during DC Line Fault, submodule overvoltage will not occur for MMC.
Except non-specifically indicating, MMC according to the present invention refers both to the MMC that part submodule has output negative voltage ability.
MMC AC/DC decoupling control method of the invention is suitable for the module that part submodule has output negative voltage ability
Change the control of multilevel converter (MMC), to guarantee the uninterrupted operation under AC fault and/or DC Line Fault.The program
Core be in current inner loop control increase DC current control so that the current inner loop control include AC current control and
DC circuit controls two kinds, and the reference value by controlling AC current control and direct current inner loop control respectively (
Referred to as instruction value), at the same control AC current control and DC current control output so that the output of AC current control and
Master of the output of DC current control collectively as the output voltage reference value of each phase bridge arm of the modularization multi-level converter
Want component.Further, it can be realized by the collective effect that AC current control and DC current control defeated to converter bridge arm
The control of voltage reference value out, and then realizing prevents inverter when DC Line Fault to be latched because of bridge arm overcurrent.
The solution of the present invention is particularly suitable for the modular multilevel that there is part submodule to have output negative voltage ability
The aerial flexible HVDC transmission system of inverter (MMC) is made of the MMC that part submodule has output negative voltage ability
Flexible HVDC transmission system, it typically is aerial DC power transmission lines, are also possible to the mixing of direct current cables route or both.Example
As flexible HVDC transmission system is maked somebody a mere figurehead at both ends or multiterminal.
The AC/DC decoupling control method of above-mentioned modularization multi-level converter of the invention is maked somebody a mere figurehead soft at both ends or multiterminal
Property DC transmission system in an application concrete scheme in, the both ends or multiterminal make somebody a mere figurehead changing for flexible HVDC transmission system
Stream station includes the modularization multi-level converter (MMC) that part submodule has output negative voltage ability, and part submodule has
The modularization multi-level converter (MMC) of output negative voltage ability is all made of above-mentioned control method and is controlled.
Above-mentioned AC/DC decoupling control method of the invention makes somebody a mere figurehead the tool of the application in flexible HVDC transmission system at both ends
In body scheme, the converter station that both ends of them make somebody a mere figurehead the every end of flexible HVDC transmission system includes that part submodule has output negative voltage
The modularization multi-level converter (MMC) of ability, the converter station that either end is specifically designated are DC voltage control station and another
One end converter station is power control station, and the part submodule in two converter stations has the modularization of output negative voltage ability
Multilevel converter (MMC) is all made of above-mentioned control method and is controlled, to pass through the direct current for reducing DC voltage control station
The reference value of voltage-controlled system is to realize the DC operating voltage for reducing the both ends and making somebody a mere figurehead flexible HVDC transmission system.
The AC/DC decoupling control method of above-mentioned modularization multi-level converter of the invention is in flexible HVDC transmission system
In an application concrete scheme in comprising when monitoring that DC Line Fault occurs, ginseng that the DC current is controlled
It examines value to be directly disposed as absorbing DC current from AC line trackside, to quickly extinguish fault electric arc.Wherein AC line trackside is inhaled
Receive -0.1~-0.3 times that DC current is preferably rated direct current.
The AC/DC decoupling control method of above-mentioned modularization multi-level converter of the invention is in flexible HVDC transmission system
In an application concrete scheme in, during restoring electricity, by either one or two of entire flexible HVDC transmission system or
The reference value of the DC current control of multiple modularization multi-level converters (MMC) is set as lesser positive value, if by one section
DC voltage is increased over certain value after time, then judges that DC Line Fault has been removed, and will then enable the control of each converter station
Device, the method for realizing the fast recovery of power supply of flexible HVDC transmission system.
The AC/DC decoupling control method of above-mentioned modularization multi-level converter of the invention has defeated in part submodule
In the application that the modularization multi-level converter of negative voltage ability is degenerated for the operation of semi-bridge type modularization multi-level converter out,
Part submodule have output negative voltage ability modularization multi-level converter using control method proposed by the invention into
Row control wherein the output for maintaining DC current control when operating normally is rated direct voltage, and is carried out in DC Line Fault
DC current control.
The foregoing is merely those skilled in the art will readily recognize that presently preferred embodiments of the present invention, not to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.
Claims (20)
1. it is negative to have output for realizing part submodule for a kind of AC/DC decoupling control method of modularization multi-level converter
Uninterrupted operation of the modularization multi-level converter of voltage capability under AC fault and/or DC Line Fault, which is characterized in that
The control method includes
Increase DC current control in current inner loop control, so that the current inner loop control includes AC current control and straight
Galvanic electricity flow control, to may make the output of output and the DC current control of the AC current control collectively as the mould
The main component of the output voltage reference value of each phase bridge arm of block multilevel converter；
The reference value of the AC current control and direct current inner loop control is controlled respectively, while controlling the alternating current
The output of flow control and DC current control, can be realized the control to the main component, and then can realize prevents direct current former
Inverter is latched because of bridge arm overcurrent when barrier；
It further include that additional DC current reference value is superimposed in the output of direct current outer loop control, wherein in submodule average capacitance electricity
The additional DC current reference value is positive value when pressure is higher than capacitance voltage upper limit value, when submodule average capacitor voltage is lower than capacitor
The additional DC current reference value is a negative value when voltage lower limit value；
Wherein, rectification direction be alternating current positive direction, modularization multi-level converter to DC line Injection Current be straight
The positive direction of galvanic electricity stream.
2. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein described
The reference value of AC current control include exchange watt current reference value with exchange two components of reactive current reference value, wherein handing over
Stream watt current reference value is set as the output of modularization multi-level converter energy hole, the modularization multi-level converter
Energy hole is for controlling the physical quantity of characterization module multilevel converter institute storage energy to corresponding reference value.
3. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein described
The reference value of DC current control is arranged to the output of direct current outer loop control, wherein the direct current outer loop control for control with
The relevant amount of dc power, the DC port voltage including dc power or modularization multi-level converter.
4. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein described
Additional DC current reference value is formed by stacking by the output of upper clipping ring and lower clipping ring, wherein the input of the upper limit width ring is
The difference of submodule average capacitor voltage and the capacitance voltage upper limit, the difference obtain the upper clipping ring after proportional, integral device
Output；The input of the lower clipping ring be submodule average capacitor voltage and capacitance voltage lower limit difference, the difference through than
The output of the lower clipping ring is obtained after example-integrator；
Wherein, the upper limit of the integrator of the upper clipping ring is set as a positive value, and lower limit is set as zero；The product of the lower clipping ring
The upper limit of device is divided to be set as zero, lower limit is set as a negative value.
5. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein described
The reference value of DC current control is arranged to the output of modularization multi-level converter energy hole, wherein the modularization is more
Level converter energy hole is for controlling the physical quantity of characterization module multilevel converter institute storage energy to corresponding
Reference value.
6. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein described
The reference value of AC current control include exchange watt current reference value with exchange two components of reactive current reference value, wherein
Exchange watt current reference value is arranged to exchange the output of active outer loop control, wherein the active outer loop control of exchange is used
In controlling relevant to active power amount, including exchanging active power, frequency, dc power, modularization multi-level converter
DC port voltage.
7. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein also wrap
It includes the superposition in the output for exchanging active outer loop control and adds active current reference value, wherein high in submodule average capacitor voltage
The additional DC current reference value is a negative value when capacitance voltage upper limit value, in submodule average capacitor voltage lower than capacitor electricity
The additional DC current reference value is a positive value when depressing limit value；
Wherein rectification direction is the positive direction of alternating current, and modularization multi-level converter (MMC) is to DC line Injection Current
For the positive direction of DC current.
8. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 7, wherein described
It adds active current reference value to be formed by stacking by the output of upper clipping ring and lower clipping ring, wherein the input of the upper limit width ring is
The difference of capacitance voltage upper limit value and submodule average capacitor voltage, the difference obtain upper clipping ring after proportional, integral device
Output, the input of the lower clipping ring are the difference of capacitance voltage lower limit and submodule average capacitor voltage, and the difference is through ratio-
The output of lower clipping ring is obtained after integrator；
Wherein the upper limit of the integrator of the upper limit width ring is set as zero, and lower limit is set as negative value, the integral of the lower clipping ring
The upper limit setting of device is positive, and lower limit is set as zero.
9. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 2 or 5, wherein
The physical quantity by characterization module multilevel converter institute storage energy, which is controlled to corresponding reference value, includes but is not limited to
Are as follows:
The energy storage summation of all submodule capacitors of modularization multi-level converter is controlled to corresponding reference value, modularization is more
The average capacitor voltage of all submodules of level converter controls to reference value, modularization multi-level converter is all exportable
The energy storage summation of the submodule capacitor of negative level is controlled to corresponding reference value, and by all tools of modularization multi-level converter
The average capacitor voltage of the submodule of standby output negative level ability is controlled to corresponding reference value.
10. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 1, wherein
The output of the AC current control is the reference value of modularization multi-level converter ac output voltage, the direct current flow control
The output of system is the half of modularization multi-level converter DC output voltage reference value.
11. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 10, wherein
In each phase the main component of bridge arm output voltage reference value be the DC current control output and AC current control it is defeated
Difference out, the main component of each phase lower bridge arm output voltage reference value are the output and alternating current flow control of DC current control
The sum of output of system.
12. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 11, wherein
When DC Line Fault occurs, the control realized to the main component is quickly reduced by the output for controlling the DC current
System, and then realizing prevents inverter when DC Line Fault to be latched because of bridge arm overcurrent.
13. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 12, wherein will
The output of DC current control is quickly reduced specifically: by DC current control in integrator reset or by its initial value
Be set as a lower limit value, it made to restart to integrate on zero initial value or negative initial value, can be realized quickly reduce it is described straight
The output of galvanic electricity flow control.
14. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 13, wherein
When DC Line Fault occurs, reduce exchange side by changing the exchange watt current reference value to zero or so, and then realizing
Modularization multi-level converter charge/discharge is given, prevents modularization multi-level converter from sustained overvoltage/under-voltage occurs.
15. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 14, wherein institute
It states and changes alternating current watt current reference value to zero or so preferably by modularization multi-level converter energy hole or active
The integrator of outer loop control is reset, so that integrator restarts to integrate and realize on zero initial value.
16. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 15, wherein
The reference value of each bridge arm output voltage also includes the loop current suppression control negated amount of output reference voltage, with described main point
Amount collectively constitutes the reference value of the bridge arm output voltage.
17. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 16, wherein
Also superposition obtained inverter direct current output port DC voltage value can be surveyed in the output that the DC current controls, thus
Improve response speed.
18. a kind of AC/DC decoupling control method of modularization multi-level converter according to claim 17, wherein
Also the DC Line Fault generation moment can be limited to DC current control by increasing the inductance of modularization multi-level converter DC side
Device starts to act the incrementss of period internal module multilevel converter DC current.
19. the AC/DC decoupling control method of modularization multi-level converter described in any one of claims 1 to 18 is two
Application in end-rack sky flexible HVDC transmission system, wherein make somebody a mere figurehead the converter station at the every end of flexible HVDC transmission system in the both ends
Has the modularization multi-level converter of output negative voltage ability including part submodule, the converter station of specified either end is
DC voltage control station and other end converter station are power control station, and the part submodule in two converter stations has output
The modularization multi-level converter of negative voltage ability is all made of control method described in any one of claim 1-18 and is controlled
System reduces the aerial flexibility in the both ends with the reference value by the DC voltage control for reducing DC voltage control station to realize
The DC operating voltage of DC transmission system.
20. the AC/DC decoupling control method of modularization multi-level converter described in any one of claims 1 to 18 is soft
Application in property DC transmission system, during restoring electricity, by any one or more of entire flexible HVDC transmission system
The reference value of the DC current control of modularization multi-level converter is set as lesser positive value, if direct current after a period of time
Voltage is increased over certain value, then judges that DC Line Fault has been removed, and will then enable the outer ring controller of each converter station, realizes
The method of the fast recovery of power supply of flexible HVDC transmission system.
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| CN107482928B (en) * | 2017-08-09 | 2018-08-24 | 冯一轩 | A kind of D.C. high voltage transmission modularization multi-level converter and its control method |
| CN107769241B (en) * | 2017-12-07 | 2020-07-28 | 南京南瑞继保电气有限公司 | Voltage and current control method and device for direct current transmission system |
| CN110603704B (en) * | 2018-02-23 | 2023-03-14 | 日立能源瑞士股份公司 | DC current control for VSC-based HVDC converters |
| CN108418221B (en) * | 2018-03-07 | 2020-01-10 | 许继电气股份有限公司 | Alternating current voltage control method and device applied to flexible direct current transmission system |
| CN108599113B (en) * | 2018-03-21 | 2022-11-25 | 中国电力科学研究院有限公司 | New energy island overvoltage control method and converter station pole control system |
| CN108512241A (en) * | 2018-03-21 | 2018-09-07 | 中国电力科学研究院有限公司 | A kind of new energy isolated island overvoltage control method and current conversion station pole control system |
| CN109193693B (en) * | 2018-10-10 | 2020-04-14 | 贵州电网有限责任公司 | Reactive power control optimization method based on flexible direct current system |
| CN109830943B (en) * | 2019-01-02 | 2020-05-19 | 华中科技大学 | Flexible direct-current power grid fault current-limiting control system, method and application |
| CN110783942B (en) * | 2019-10-10 | 2021-04-20 | 华中科技大学 | Fault current-limiting control method and system for MMC type flexible direct-current power grid |
| WO2022008085A1 (en) * | 2020-07-10 | 2022-01-13 | Hitachi Energy Switzerland Ag | Control of a modular multilevel converter of a full bridge or mixed arm type in case of a dc line disturbance |
| CN111812503B (en) * | 2020-07-17 | 2022-12-16 | 北京四方继保自动化股份有限公司 | Testing method and testing system suitable for flexible direct current converter valve |
| CN111864785B (en) * | 2020-08-14 | 2021-12-03 | 华中科技大学 | AC/DC fault-resistant AC side cascade type hybrid MMC topology control method |
| CN111934340B (en) * | 2020-08-24 | 2021-11-19 | 华中科技大学 | Adaptive power-voltage droop control method and system for direct current transmission system |
| CN113394772A (en) * | 2021-06-16 | 2021-09-14 | 南方电网科学研究院有限责任公司 | DC fault clearing control method and device for mixed MMC and storage medium |
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