CN106357141A - Reduced voltage operation method for hybrid MMC-HVDC (modular multilevel converter based high voltage direct current) system - Google Patents
Reduced voltage operation method for hybrid MMC-HVDC (modular multilevel converter based high voltage direct current) system Download PDFInfo
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- CN106357141A CN106357141A CN201610865144.2A CN201610865144A CN106357141A CN 106357141 A CN106357141 A CN 106357141A CN 201610865144 A CN201610865144 A CN 201610865144A CN 106357141 A CN106357141 A CN 106357141A
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- mixed type
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- brachium pontis
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- type mmc
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
Abstract
The invention discloses a reduced voltage operation method for a hybrid MMC-HVDC (modular multilevel converter based high voltage direct current) system. Full-bridge sub-modules exist in a hybrid MMC, so that negative voltage can be output by bridge arms to achieve flexibility and controllability of the voltage of the alternating current side of the hybrid MMC. The sum of the output voltage of the upper and lower bridge arms is regulated to regulate the output voltage of the direct current side of the hybrid MMC. The difference between the output voltage of the upper and lower bridge arms is regulated to regulate the alternating current internal potential output by the hybrid MMC, namely regulating the output voltage of the alternating current side of the hybrid MMC to regulate active power transmitted by the hybrid MMC and reactive power exchanged with an alternating current power grid to ensure safe and reliable operation of an alternating and direct current system. Meanwhile, during reduced voltage operation, low-frequency loop current is injected to the bridge arms of the hybrid MMC, so that the problem of incapability of half-bridge sub-modules in voltage balancing when relatively higher active power is output under relatively lower direct current voltage is solved, the operation range of the hybrid MMC under low direct current voltage is extended, and more active power can be transmitted.
Description
Technical field
The invention belongs to multilevel power electronic converter technical field, it is based on mixed type mmc more particularly, to a kind of
Hvdc system brownout operation method.
Background technology
Under extreme weather conditions, such as thunderstorm, heavy rain, snowstorm etc., DC transmission system needs to reduce DC voltage
To reduce the probability that line fault occurs.But, due to the restriction of voltage modulated ratio, the reduction of DC voltage can lead to the change of current
The reduction of device output AC voltage, thus lead to inverter to absorb substantial amounts of reactive power from connected electrical network, to alternating current-direct current system
The safe and stable operation of system impacts.Meanwhile, the reduction of DC voltage, can lead to straight-flow system through-put power to reduce, system
Line loss increases, and reduces the operational efficiency of straight-flow system.For above reason, current flexible direct current power transmission system, straight
Stream voltage step-down operation aspect is limited in one's ability, and the ability of reply extreme weather challenge is also than relatively limited.
D.C. high voltage transmission (modular multilevel based on mixing mould massing multilevel converter
Converter based high voltage direct current, mmc-hvdc) system is because it is in system loss, capacity
Upgrading, electromagnetic compatibility, the advantage of the aspect such as fault management, quickly grow in China, the hvdc system based on mixed type mmc is used
In the extreme weather that copes with challenges, there is very major and immediate significance.
Content of the invention
For disadvantages described above, the invention provides a kind of brownout operation method of the hvdc system based on mixed type mmc, purport
In solving due to existing inverter, DC voltage and AC voltage do not decouple and lead to existing flexible DC power transmission system
During system brownout operation, inverter output AC voltage also reduces so that flexible direct current power transmission system absorbs idle work(in a large number from electrical network
Rate is thus affect the safe and stable operation of AC network.
For achieving the above object, the invention provides a kind of brownout operation method of the hvdc system based on mixed type mmc,
The upper brachium pontis of described mixed type mmc comprises multiple full-bridge submodules and multiple half-bridge submodule, and lower brachium pontis includes multiple full-bridge
Module and multiple half-bridge submodule, comprise the following steps:
(1) the DC voltage level v ' that straight-flow system must drop to is determined according to external environment conditiondc；
(2) determine that mixed type mmc AC exports according to the active power of needs transmission during brownout operation and reactive power
Voltage vj；
(3) pass through to control full-bridge submodule and half-bridge submodule to turn on quantity, brachium pontis output voltage and lower brachium pontis in regulation
Output voltage sum meets formula vnj+vpj=v 'dc, make mixed type mmc DC side output voltage be v 'dc；
(4) pass through to control full-bridge submodule and half-bridge submodule to turn on quantity, brachium pontis output voltage and lower brachium pontis in regulation
The difference of output voltage meets formulaMixed type mmc AC output voltage is made to be vj；
In formula, v 'dcFor mixed type mmc DC side output voltage, v during brownout operationjDefeated for mixed type mmc during brownout operation
The exchange built-in potential going out, vpjFor connecting the upper brachium pontis output voltage of alternating current j phase, v in mixed type mmcnjFor in mixed type mmc
Connect the lower brachium pontis output voltage of alternating current j phase, j=a, b, c, and a, b, c represent alternating current a, b, c phase.
Due to the presence of full-bridge submodule in mixed type mmc, mixed type mmc brachium pontis output negative voltage can be made, make mixing
Type mmc DC side output voltage reduce do not interfere with mixed type mmc output exchange built-in potential, by adjust full-bridge submodule and
The quantity of half-bridge submodule conducting changes upper brachium pontis output voltage and lower brachium pontis output voltage sum, realizes adjusting mixed type mmc
DC side output voltage, after mixed type mmc DC side sets up voltage, by adjusting full-bridge submodule and the conducting of half-bridge submodule
Quantity change the difference of upper brachium pontis output voltage and lower brachium pontis output voltage, realize adjusting the exchange built-in potential of mixing mmc output,
Thus changing mixed type mmc AC output voltage, realizing mixed type mmc transmitting active power and reactive power is flexibly controlled.
A progressive ground, also comprises the steps: after step (4)
(5) if v 'dc≤vj, then inject low frequency circulation in the upper brachium pontis and lower brachium pontis of mixed type mmc, otherwise, not to mixed
Low frequency circulation is injected in the upper brachium pontis of mould assembly mmc and lower brachium pontis；
In formula, v 'dcFor mixed type mmc DC side output voltage, v during brownout operationjHand over for mixed type mmc during brownout operation
Stream side output voltage；
By inject low frequency circulation change the direction of bridge arm current by force so as to have just have negative, solve half-bridge submodule equal
Pressure problem, improves the conveying capacity of mixed type mmc active power, expands mixed type mmc range of operation.
Further, upper brachium pontis and the lower brachium pontis injection low frequency circulation of normal direction mixed type mmc are injected using common-mode voltage, that is,
By being superimposed corresponding common-mode voltage component in upper and lower bridge arm equivalent voltage source output voltage reference value, this voltage is made to be added in bridge
On arm reactor, brachium pontis produces corresponding electric current, realize the injection of brachium pontis circulation.
Further, the frequency of injection low frequency circulation is 15hz～25hz, and half-bridge submodule can be made to have the time of abundance
All press, voltage equalizing is best.
Further, the size of injection low frequency circulation is
After ensureing injection low frequency circulation, bridge arm current has just has negative, realizes the good of half-bridge submodule and all presses, and bridge arm current is not again simultaneously
Exceed the maximum current capacity of brachium pontis switching device.
In formula, the active power that p exports for mixed type mmc, the reactive power that q exports for mixed type mmc, vsmFor AC
The amplitude of voltage, icFor the amplitude of low frequency circulation, v 'dcFor the mixed type mmc DC side output voltage after brownout operation, ilimFor
The maximum current capacity of all brachium pontis breaker in middle pipes.
By the contemplated above technical scheme of the present invention, compared with prior art, there is a following technique effect:
(1) present invention provides the brownout operation method of the hvdc system based on mixed type mmc, makes due in mixed type mmc
With full-bridge submodule, enable mixed type mmc brachium pontis to export negative voltage it is achieved that mixed type mmc AC output voltage with
The decoupling of DC side output voltage, when DC voltage reduces, can keep mixed type mmc AC output voltage flexibly may be used
Control, by adjusting the quantity of full-bridge submodule and half-bridge submodule input in mixed type mmc, changes mixed type mmc AC defeated
Go out voltage and DC side output voltage, so that mixed type mmc is not only needed from AC absorbing reactive power, and can be to friendship
Stream electrical network provides reactive power support, is capable of controlling reactive power while DC side output voltage reduces.
(2) during DC voltage brownout operation, by injecting low frequency circulation to mixed type mmc brachium pontis, solve half-bridge
When module exports larger active power under compared with low dc voltage cannot equal pressures problem, expand mixed type under low dc voltage
The range of operation of mmc is so as to more active power can be transmitted.
Brief description
In the brownout operation method based on the hvdc system of mixed type mmc that Fig. 1 provides for the present invention, mixed type mmc opens up
Flutter structure；
In the brownout operation method based on the hvdc system of mixed type mmc that Fig. 2 provides for the present invention mixed type mmc etc.
Effect circuit；
The flow chart of the brownout operation method of the hvdc system based on mixed type mmc that Fig. 3 provides for the present invention；
Fig. 4 provides the brownout operation method of the hvdc system based on mixed type mmc of the first emulation embodiment for the present invention
Performance map, wherein, the DC voltage figure that (a) exports for mixed type mmc, the AC voltage that (b) exports for mixed type mmc
Figure, the ac-side current figure that (c) exports for mixed type mmc, the active power figure that (d) exports for mixed type mmc, (e) is mixing
The reactive power figure of type mmc output；
Fig. 5 provides the brownout operation method of the hvdc system based on mixed type mmc of the second emulation embodiment for the present invention
Performance map, wherein, active power and reactive power figure that (a) exports for mixed type mmc, (b) is full-bridge in mixed type mmc
Module capacitance voltage pattern, (c) is half-bridge submodule capacitor voltage figure in mixed type mmc, and (d) is mixed type mmc bridge arm current figure；
Fig. 6 provides the brownout operation method of the hvdc system based on mixed type mmc of the 3rd emulation embodiment for the present invention
Performance map, wherein, active power and reactive power figure that (a) exports for mixed type mmc, (b) is full-bridge in mixed type mmc
Module capacitance voltage pattern, (c) is half-bridge submodule capacitor voltage figure in mixed type mmc, and (d) is mixed type mmc bridge arm current figure.
Specific embodiment
In order that the objects, technical solutions and advantages of the present invention become more apparent, below in conjunction with drawings and Examples, right
The present invention is further elaborated.It should be appreciated that specific embodiment described herein is only in order to explain the present invention, and
It is not used in the restriction present invention.
It is illustrated in figure 1 the topological structure of mixed type mmc, the upper brachium pontis connecting alternating current j phase includes multiple full-bridge submodules
Block and multiple half-bridge submodule, the lower brachium pontis connecting alternating current j phase includes multiple full-bridge submodules and multiple half-bridge submodule, its
Middle j=a, b, c, and a, b, c represent alternating current a, b, c phase, and half-bridge submodule can export positive level and zero level, full-bridge submodule
Block can export positive level, negative level and zero level.Because full-bridge submodule can export negative level, make mixed type mmc direct current
Side output voltage exchanges built-in potential decoupling with output, when DC voltage reduces, mixed type mmc AC can be kept defeated
Go out voltage flexibly controlled.
It is illustrated in figure 2 the equivalent circuit of mixed type mmc, connect all full-bridge submodules of upper brachium pontis and the half-bridge of j phase
Submodule is equivalent to voltage source vpj, connect all full-bridge submodules of lower brachium pontis of j phase and half-bridge submodule be equivalent to voltage source
vnj, wherein, j=a, b, c, and a, b, c represent a of alternating current, b, c phase respectively, and modularization multi-level converter passes through AC
Transformator connects AC network.
As shown in figure 3, the brownout operation method of the hvdc system based on mixed type mmc of present invention offer includes walking as follows
Rapid:
(1) the DC voltage level v ' that straight-flow system must drop to is determined according to external environment conditiondc；
(2) determine that mixed type mmc AC exports according to the active power of needs transmission during brownout operation and reactive power
Voltage vj；
(3) pass through to control full-bridge submodule and half-bridge submodule to turn on quantity, brachium pontis output voltage and lower brachium pontis in regulation
Output voltage sum meets formula vnj+vpj=v 'dc, make mixed type mmc DC side output voltage be v 'dc, in formula, v 'dcFor fall
Mixed type mmc DC side output voltage when pressure is run, vpjFor connecting the upper brachium pontis output voltage of alternating current j phase in mixed type mmc,
vnjFor connecting the lower brachium pontis output voltage of alternating current j phase, j=a, b, c, and a in mixed type mmc, b, c represent a, b, c phase.
Upper brachium pontis output voltage is changed by the quantity adjusting full-bridge submodule and the conducting of half-bridge submodule and lower brachium pontis is defeated
Go out voltage sum, realize adjusting mixed type mmc DC side output voltage；Due to the presence of full-bridge submodule in mixed type mmc, make
Mixed type mmc brachium pontis can export negative dc voltage, make mixed type mmc DC side output voltage with output exchange built-in potential solution
Coupling, that is, reduce mixed type mmc DC voltage and will not change mixed type mmc AC output voltage.
(4) pass through to control the quantity of full-bridge submodule and the conducting of half-bridge submodule, brachium pontis output voltage and Xia Qiao in regulation
The difference of arm output voltage meets formulaMixed type mmc AC output voltage is made to be vj；
In formula, vjFor the exchange built-in potential of mixed type mmc output during brownout operation, set up DC voltage in mixed type mmc
Afterwards, then adjust full-bridge submodule and the conducting of half-bridge submodule quantity change upper brachium pontis output voltage and lower brachium pontis output voltage it
Difference, realizes adjusting the exchange built-in potential of mixing mmc output, and realizing adjusting mixed type mmc AC output voltage is vjSo that it is mixed
Mould assembly mmc in transmitting active power, can adjust the reactive power exchanging to AC network it is ensured that the safety of AC network simultaneously
Stable operation.
In the embodiment that the present invention provides, after step (4), if also comprising the steps:, DC side output voltage is little
In or be equal to AC output voltage, then to brachium pontis mixed type mmc in and lower brachium pontis injection low frequency circulation, otherwise, not to mixing
Brachium pontis and lower brachium pontis injection low frequency circulation in type mmc.If DC side output voltage is more than AC output electricity after brownout operation
Press, now half-bridge submodule can well all be pressed it is not necessary to inject low frequency circulation again in brachium pontis；If direct current after brownout operation
Side output voltage is less than or equal to AC output voltage, and with the raising of through-put power, bridge arm current can become single direction,
Just it is always or is always negative, lead to half-bridge submodule persistently to charge or continuous discharge is it is impossible to all press, now need in brachium pontis
Middle injection low frequency circulation, changing the direction of bridge arm current by force by injection low frequency circulation so as to have just has negative, solution half-bridge
Module voltage-sharing, improves the active power conveying capacity of mixed type mmc.
The method for implanting of the embodiment medium and low frequency circulation that the present invention provides is common-mode voltage injection method, that is, pass through in upper and lower bridge
It is superimposed corresponding common-mode voltage component in arm equivalent voltage source output voltage reference value, make this voltage pass through brachium pontis reactor,
Produce corresponding electric current in brachium pontis, realize the injection of brachium pontis low frequency circulation.
The frequency of injection low frequency circulation is 15hz～25hz, the time that half-bridge submodule has abundance can be made all to press, make all
Pressure effect is best.
After injection low frequency circulation, upper bridge arm current is represented by:
Lower bridge arm current is represented by:
In formula, ijpThe active power exporting for mixed type mmc for upper bridge arm current, p, q for mixed type mmc export idle
Power, vsmFor AC voltage magnitude, w is mains frequency, ψjFor bridge arm current phase place, t is the time, v 'dcAfter brownout operation
Mixed type mmc DC side output voltage, icFor injecting low frequency circulation amplitude, ijnFor lower bridge arm current, j=a, b, c, and a, b,
C represents a, b, c phase.
Must assure that all bridge arm current just to have to have negative after injection low frequency circulation, that is, need to meet following formula:
It is desirable to all bridge arm current must not exceed the through-flow energy of maximum of brachium pontis switching device it is desirable to meet after injection circulation
Following formula:
In formula, ilimMaximum current capacity for brachium pontis breaker in middle pipe.
Need to meet by above-mentioned low frequency circulation amplitude size of can injecting:
The present invention provides emulation embodiment, that is, pass through the hvdc system based on mixed type mmc for the software emulation, in mixed type
In the hvdc system of mmc, in every phase, the number ratio of brachium pontis full-bridge submodule and half-bridge submodule is 1:1, is 10, electric capacity
Voltage ratio is 1:1, is 1kv, and in brachium pontis under every phase, the number ratio of full-bridge submodule and half-bridge submodule is 1:1, is
10, capacitance voltage ratio is 1:1, is 1kv.DC side rated voltage v during normal operationdc0=20kv, exchange side line electricity
Press as 10kv, transmission rated active power is 20mw, rated reactive power 4mvar.
Emulation embodiment one
After brownout operation, DC voltage requires to be changed into 15kv, and the active power of transmission is 15mw, and reactive power is transported in blood pressure lowering
During row, 6mvar is adjusted to by 4mvar.As shown in figure 3, by the full-bridge submodule changing upper brachium pontis and conducting in lower brachium pontis
With the quantity of half-bridge submodule, brachium pontis output voltage and lower brachium pontis output voltage sum in change, change the output of mixed type mmc
DC voltage, in Fig. 4 (a), DC voltage drops to 15kv by 20kv, subsequently turns on by the upper brachium pontis of change and lower brachium pontis again
Full-bridge submodule and half-bridge submodule quantity so that upper brachium pontis output voltage and lower brachium pontis output voltage difference keep not
Become so that the exchange built-in potential of mixed type mmc output is not changed in, that is, shown in alternating current such as Fig. 4 (b) of mixed type mmc output
It is not changed in, illustrates that mixed type mmc AC output voltage is controlled, such as shown in Fig. 4 (d), through-put power becomes 15mw by 20mw,
As shown in Fig. 4 (c), after through-put power reduces, ac-side current diminishes, such as shown in Fig. 4 (e), to the idle work(of electrical network offer
Rate is also flexibly controlled, brownout operation for a period of time after, reactive power can automatically on be transferred to 6mvar.
Emulation embodiment two
After brownout operation, DC voltage requires to be changed into 5kv, and transmission reactive power keeps constant, and reactive power is 4mvar,
The active power of transmission is reduced to 5mw.By changing the full-bridge submodule of upper brachium pontis and conducting in lower brachium pontis and half-bridge submodule
Quantity, brachium pontis output voltage and lower brachium pontis output voltage sum in change, change mixed type mmc DC side output voltage, by
20kv is changed into 5kv, and now pressure drop is larger, sub with the full-bridge submodule of conducting in lower brachium pontis and half-bridge by changing upper brachium pontis again
The quantity of module, so that the difference of upper brachium pontis output voltage and lower brachium pontis output voltage is constant, makes in the exchange of mixed type mmc output
Potential keeps constant, such as Fig. 5 (a), and active power p is changed into 5mw from 20mw, and reactive power keeps constant, such as shown in Fig. 5 (d), by
In DC voltage pressure drop larger so that bridge arm current is always negative, full-bridge submodule as shown in Fig. 5 (b) can keep good
All press, but as shown in Fig. 5 (c) half-bridge submodule due to continuous discharge it is impossible to all press, lead to half-bridge submodule capacitor voltage continue
Reduce so that mixed type mmc cannot long-play, impact system stability.Emulation embodiment three
After brownout operation, DC voltage requires to be changed into 5kv, and transmission reactive power keeps constant, and reactive power is 4mvar,
The active power of transmission is 5mw.By changing upper brachium pontis and the full-bridge submodule of conducting in lower brachium pontis and the number of half-bridge submodule
Amount, brachium pontis output voltage and lower brachium pontis output voltage sum in change, change mixed type mmc DC side output voltage, by 20kv
Be changed into 5kv, by change the full-bridge submodule of conducting and the quantity of half-bridge submodule in upper brachium pontis and lower brachium pontis again so that on
The difference of brachium pontis output voltage and lower brachium pontis output voltage keeps constant, makes the exchange built-in potential that mixed type mmc exports keep constant,
As Fig. 6 (a), active power p is changed into 5mw from 20mw, and reactive power keeps constant, makes bridge by injection low frequency circulation in brachium pontis
Arm electric current changes direction, and such as shown in Fig. 6 (d), even if larger in DC voltage pressure drop, bridge arm current is due to the note of low frequency circulation
Entering to become to have just has negative, and full-bridge submodule as shown in Fig. 6 (b) still can keep well all pressing, simultaneously half as shown in Fig. 6 (c)
Bridge submodule also can well all be pressed, and mixed type mmc can keep safe operation it is ensured that the stability of system.
As it will be easily appreciated by one skilled in the art that the foregoing is only presently preferred embodiments of the present invention, not in order to
Limit the present invention, all any modification, equivalent and improvement made within the spirit and principles in the present invention etc., all should comprise
Within protection scope of the present invention.
Claims (5)
1. a kind of brownout operation method of the hvdc system based on mixed type mmc, the upper brachium pontis of described mixed type mmc comprises multiple
Full-bridge submodule and multiple half-bridge submodule, lower brachium pontis includes multiple full-bridge submodules and multiple half-bridge submodule, and its feature exists
In comprising the following steps:
(1) the DC voltage level v ' that straight-flow system must drop to is determined according to external environment conditiondc；
(2) mixed type mmc AC output voltage is determined according to the active power of needs transmission and reactive power during brownout operation
vj；
(3) pass through to control full-bridge submodule and half-bridge submodule to turn on quantity, brachium pontis output voltage and the output of lower brachium pontis in regulation
Voltage sum meets formula vnj+vpj=v 'c, make mixed type mmc DC side output voltage be v 'dc,
(4) pass through to control full-bridge submodule and half-bridge submodule to turn on quantity, brachium pontis output voltage and the output of lower brachium pontis in regulation
Difference in voltage meets formulaMixed type mmc AC output voltage is made to be vj；
In formula, v 'dcFor mixed type mmc DC side output voltage, v during brownout operationjFor mixed type mmc AC during brownout operation
Output voltage, vpjFor connecting the upper brachium pontis output voltage of alternating current j phase, v in mixed type mmcnjHand over for connecting in mixed type mmc
The lower brachium pontis output voltage of the electric j phase of stream, j=a, b, c, and a, b, c represent a, b, c phase.
2. brownout operation method according to claim 1 is it is characterised in that also comprise the steps: after step (4)
(5) if v 'dc≤vj, then inject low frequency circulation in the upper brachium pontis and lower brachium pontis of mixed type mmc, otherwise, not to mixed type
Low frequency circulation is injected in the upper brachium pontis of mmc and lower brachium pontis；
v′dcFor mixed type mmc DC side output voltage, v during brownout operationjExport for mixed type mmc AC during brownout operation
Voltage.
3. brownout operation method according to claim 2 is it is characterised in that inject normal direction mixed type using common-mode voltage
The upper brachium pontis of mmc and lower brachium pontis injection low frequency circulation.
4. brownout operation method according to claim 2 it is characterised in that described low frequency circulation frequency be 15hz～
25hz.
5. brownout operation method according to claim 2 is it is characterised in that the size of described low frequency circulation is
In formula, the active power that p exports for mixed type mmc, the reactive power that q exports for mixed type mmc, vsmFor AC voltage
Amplitude, icFor the amplitude of low frequency circulation, v 'dcFor the mixed type mmc DC side output voltage after brownout operation, ilimFor all bridges
The maximum current capacity of arm breaker in middle pipe.
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| CN107634659A (en) * | 2017-09-13 | 2018-01-26 | 华中科技大学 | A kind of control method of expansion mixed type MMC operation areas |
| CN109861570A (en) * | 2019-04-02 | 2019-06-07 | 南京师范大学 | A kind of low frequency circulation inhibition method of carrier wave stacking pulsewidth modulation lower module multi-level converter |
| CN110474341A (en) * | 2019-08-07 | 2019-11-19 | 中国南方电网有限责任公司超高压输电公司广州局 | A kind of mixed type MMC flexible direct-current transmission system brownout operation control method |
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| CN107634659A (en) * | 2017-09-13 | 2018-01-26 | 华中科技大学 | A kind of control method of expansion mixed type MMC operation areas |
| CN109861570A (en) * | 2019-04-02 | 2019-06-07 | 南京师范大学 | A kind of low frequency circulation inhibition method of carrier wave stacking pulsewidth modulation lower module multi-level converter |
| CN109861570B (en) * | 2019-04-02 | 2020-04-03 | 南京师范大学 | Low-frequency circulating current suppression method of modular multilevel converter under carrier stacked pulse width modulation |
| CN110474341A (en) * | 2019-08-07 | 2019-11-19 | 中国南方电网有限责任公司超高压输电公司广州局 | A kind of mixed type MMC flexible direct-current transmission system brownout operation control method |
| CN110474341B (en) * | 2019-08-07 | 2020-09-22 | 中国南方电网有限责任公司超高压输电公司广州局 | Voltage reduction operation control method for hybrid MMC flexible direct current power transmission system |
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