CN106357141B - A kind of brownout operation method of the HVDC systems based on mixed type MMC - Google Patents
A kind of brownout operation method of the HVDC systems based on mixed type MMC Download PDFInfo
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- CN106357141B CN106357141B CN201610865144.2A CN201610865144A CN106357141B CN 106357141 B CN106357141 B CN 106357141B CN 201610865144 A CN201610865144 A CN 201610865144A CN 106357141 B CN106357141 B CN 106357141B
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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 kind of brownout operation methods of the HVDC systems based on mixed type MMC,Since there are full-bridge submodules in mixed type MMC,Its bridge arm is enable to export negative voltage,Realize that mixed type MMC exchange side voltages are flexibly controllable,By adjusting the sum of upper and lower bridge arm output voltage,It realizes and adjusts mixed type MMC DC side output voltages,Adjust the difference of upper and lower bridge arm output voltage,Realize the exchange built-in potential for adjusting mixed type MMC outputs,Adjust mixed type MMC exchange side output voltages,Realize the reactive power for adjusting the active power of mixed type MMC transmission and being exchanged to AC network,Ensure the safe and stable operation of ac and dc systems,Simultaneously,During brownout operation,By injecting low frequency circulation to mixed type MMC bridge arms,Solve the problems, such as that half-bridge submodule can not be pressed compared with when exporting larger active power under low dc voltage,Expand the range of operation of mixed type MMC under low dc voltage,More active power can be transmitted.
Description
Technical field
The invention belongs to multilevel power electronic converter technical fields, and mixed type MMC is based on more particularly, to one kind
HVDC systems 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 voltage modulated than restriction, the reduction of DC voltage can lead to the change of current
The reduction of device output AC voltage absorbs a large amount of reactive power, to alternating current-direct current system so as to cause transverter from connected power grid
The safe and stable operation of system impacts.Meanwhile the reduction of DC voltage, the reduction of straight-flow system transimission power, system can be caused
Line loss increases, and reduces the operational efficiency of straight-flow system.For more than reason, current flexible direct current power transmission system, straight
Ability is limited in terms of flowing voltage step-down operation, copes with the ability of extreme weather challenge also than relatively limited.
D.C. high voltage transmission (Modular Multilevel based on mixed type module multilevel converter
Converter Based High Voltage Direct Current, MMC-HVDC) system is because it is in system loss, capacity
The advantage of upgrading, electromagnetic compatibility, fault management etc., quickly grows in China, and the HVDC systems based on mixed type MMC are used
There is very major and immediate significance in the extreme weather that copes with challenges.
Invention content
For disadvantages described above, the present invention provides a kind of brownout operation method of the HVDC systems based on mixed type MMC, purports
DC voltage is not decoupled with exchange side voltage in solving due to existing transverter leads to existing flexible DC power transmission system
Transverter output AC voltage also reduces during system brownout operation so that flexible direct current power transmission system absorbs a large amount of idle work(from power grid
Rate is so as to influence the safe and stable operation of AC network.
To achieve the above object, the present invention provides a kind of brownout operation method of the HVDC systems based on mixed type MMC,
The upper bridge arm of the mixed type MMC includes multiple full-bridge submodules and multiple half-bridge submodules, and lower bridge arm includes multiple full-bridges
Module and multiple half-bridge submodules, include the following steps：
(1) DC voltage level V' that straight-flow system must drop to is determined according to external environmentdc；
(2) determine that mixed type MMC exchange side exports according to the active power and reactive power that needs transmit during brownout operation
Voltage vj；
(3) quantity is connected by controlling full-bridge submodule and half-bridge submodule, bridge arm output voltage and lower bridge arm in adjusting
The sum of output voltage meets formula vnj+vpj=V'dc, it is V' to make mixed type MMC DC sides output voltagedc；
(4) quantity is connected by controlling full-bridge submodule and half-bridge submodule, bridge arm output voltage and lower bridge arm in adjusting
The difference of output voltage meets formulaIt is v to make mixed type MMC exchange side output voltagej；
In formula, V'dcMixed type MMC DC side output voltages, v during for brownout operationjMixed type MMC is handed over during for brownout operation
Flow side output voltage, vpjTo connect the upper bridge arm output voltage of alternating current j phases, v in mixed type MMCnjTo connect in mixed type MMC
It meets the lower bridge arm output voltage of alternating current j phases, j=a, b, c, and a, b, c and represents alternating current A, B, C phase.
Due to the presence of full-bridge submodule in mixed type MMC, mixed type MMC bridge arms can be made to export negative voltage, make mixing
The reduction of type MMC DC sides output voltage does not interfere with mixed type MMC exchange side output voltages, by adjusting full-bridge submodule and half
The quantity of bridge submodule conducting changes upper the sum of bridge arm output voltage and lower bridge arm output voltage, realizes that adjusting mixed type MMC is straight
Side output voltage is flowed, after mixed type MMC DC sides establish voltage, is connected by adjusting full-bridge submodule and half-bridge submodule
Quantity changes the difference of upper bridge arm output voltage and lower bridge arm output voltage, realizes and adjusts mixing MMC exchange side output voltages, so as to
Change mixed type MMC exchange side output voltages, realize that mixed type MMC transmitting active powers and reactive power are flexibly controllable.
One ground of progress, following steps are further included after step (4)：
(5) if V'dc≤Vjm, then low frequency circulation is injected into the upper bridge arm and lower bridge arm of mixed type MMC, otherwise, not to mixed
Low frequency circulation is injected in the upper bridge arm and lower bridge arm of mould assembly MMC；
In formula, V'dcMixed type MMC DC side output voltages, V during for brownout operationjMixed type MMC is handed over during for brownout operation
Flow side output voltage, VjmMixed type MMC exchange side output voltage amplitudes during for brownout operation.
Change the direction of bridge arm current by force by injecting low frequency circulation, make its have just have it is negative, solve half-bridge submodule it is equal
Pressure problem improves the conveying capacity of mixed type MMC active power, expands mixed type MMC ranges of operation.
Further, low frequency circulation is injected using the upper bridge arm and lower bridge arm of common-mode voltage injection normal direction mixed type MMC, i.e.,
By being superimposed corresponding common-mode voltage component in upper and lower bridge arm equivalent voltage source output voltage reference value, the voltage is made to be added in bridge
On arm reactor, corresponding electric current is generated in bridge arm, realizes the injection of bridge arm circulation.
Further, the frequency of injection low frequency circulation is 15Hz~25Hz, and half-bridge submodule can be made to have the sufficient time
It presses, voltage equalizing is best.
Further, the size of injection low frequency circulation is
Ensureing after injection low frequency circulation bridge arm current has just and has negative, realizes that the good of half-bridge submodule is pressed, while bridge arm current is again not
More than the maximum current capacity of bridge arm switching device.
In formula, active power of the P for mixed type MMC outputs, reactive powers of the Q for mixed type MMC outputs, VsmFor exchange side
The amplitude of voltage, ICFor the amplitude of low frequency circulation, V'dcFor the mixed type MMC DC side output voltages after brownout operation, IlimFor
The maximum current capacity of switching tube in all bridge arms.
By the above technical scheme conceived by the present invention, compared with prior art, there is following technique effect：
(1) present invention provides the brownout operation method of the HVDC systems based on mixed type MMC, due to making in mixed type MMC
With full-bridge submodule, mixed type MMC bridge arms is enable to export negative voltage, realize mixed type MMC exchange side output voltage with
The decoupling of DC side output voltage when DC voltage reduces, can keep mixed type MMC exchange side output voltages flexibly may be used
By adjusting the quantity that full-bridge submodule and half-bridge submodule are put into mixed type MMC, it is defeated to change mixed type MMC exchange side for control
Go out voltage and DC side output voltage, mixed type MMC is made not need to not only from exchange side absorbing reactive power, but also can be to friendship
Galvanic electricity net provides reactive power support, can realize and control reactive power while DC side output voltage reduces.
(2) during DC voltage brownout operation, by injecting low frequency circulation to mixed type MMC bridge arms, half-bridge is solved
Module expands mixed type under low dc voltage compared with can not be pressed when exporting larger active power under low dc voltage the problem of
The range of operation of MMC can transmit more active power.
Description of the drawings
Fig. 1 be HVDC systems provided by the invention based on mixed type MMC brownout operation method in mixed type MMC open up
Flutter structure；
Fig. 2 be the HVDC systems provided by the invention based on mixed type MMC brownout operation method in mixed type MMC etc.
Imitate circuit；
Fig. 3 is the flow chart of the brownout operation method of the HVDC systems provided by the invention based on mixed type MMC；
Fig. 4 provides the brownout operation method of the HVDC systems based on mixed type MMC of the first emulation embodiment for the present invention
Performance map, wherein, (a) be mixed type MMC output DC voltage figure, (b) be mixed type MMC output exchange side voltage
Figure, (c) are the ac-side current figure of mixed type MMC outputs, and (d) is the active power figure of mixed type MMC outputs, and (e) is mixing
The reactive power figure of type MMC outputs；
Fig. 5 provides the brownout operation method of the HVDC systems based on mixed type MMC of the second emulation embodiment for the present invention
Performance map, wherein, (a) be mixed type MMC output active power and reactive power figure, (b) be mixed type MMC in full-bridge
Module capacitance voltage pattern, (c) are half-bridge submodule capacitor voltage figure in mixed type MMC, and (d) is mixed type MMC bridge arm current figures；
Fig. 6 provides the brownout operation method of the HVDC systems based on mixed type MMC of third emulation embodiment for the present invention
Performance map, wherein, (a) be mixed type MMC output active power and reactive power figure, (b) be mixed type MMC in full-bridge
Module capacitance voltage pattern, (c) are half-bridge submodule capacitor voltage figure in mixed type MMC, and (d) is mixed type MMC bridge arm current figures.
Specific embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, with reference to the accompanying drawings and embodiments, it is 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.
It is the topological structure of mixed type MMC as shown in Figure 1, the upper bridge arm of connection alternating current j phases includes multiple full-bridge submodules
Block and multiple half-bridge submodules, the lower bridge arm of connection alternating current j phases include multiple full-bridge submodules and multiple half-bridge submodules,
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.Since full-bridge submodule can export negative level, make mixed type MMC direct currents
Side output voltage is decoupled with exchange side output voltage, when DC voltage reduces, mixed type MMC exchange side can be kept to export
Voltage is flexibly controllable.
The equivalent circuit of mixed type MMC is illustrated in figure 2, connects all full-bridge submodules and half-bridge of the upper bridge arm of j phases
Submodule is equivalent to voltage source Vpj, all full-bridge submodules and half-bridge submodule that connect the lower bridge arm of j phases are equivalent to voltage source
Vnj, wherein, j=a, b, c, and a, b, c represent the A of alternating current respectively, B, C phases, modularization multi-level converter passes through exchange side
Transformer connects AC network.
As shown in figure 3, the brownout operation method of the HVDC systems provided by the invention based on mixed type MMC includes following step
Suddenly：
(1) DC voltage level V' that straight-flow system must drop to is determined according to external environmentdc；
(2) determine that mixed type MMC exchange side exports according to the active power and reactive power that needs transmit during brownout operation
Voltage vj；
(3) quantity is connected by controlling full-bridge submodule and half-bridge submodule, bridge arm output voltage and lower bridge arm in adjusting
The sum of output voltage meets formula vnj+vpj=V'dc, it is V' to make mixed type MMC DC sides output voltagedc, in formula, V'dcFor drop
Mixed type MMC DC side output voltages during pressure operation, vpjTo connect the upper bridge arm output voltage of alternating current j phases in mixed type MMC,
vnjTo connect the lower bridge arm output voltage of alternating current j phases, j=a, b, c in mixed type MMC, and a, b, c represent A, B, C phases.
The quantity be connected by adjusting full-bridge submodule and half-bridge submodule changes upper bridge arm output voltage and lower bridge arm is defeated
Go out the sum of voltage, realize and adjust mixed type MMC DC side output voltages；Due to the presence of full-bridge submodule in mixed type MMC, make
Mixed type MMC bridge arms can export negative dc voltage, decouple mixed type MMC DC sides output voltage and exchange side output voltage,
Mixed type MMC exchange side output voltages will not be changed by reducing mixed type MMC DC voltages.
(4) by the quantity that full-bridge submodule and half-bridge submodule is controlled to be connected, bridge arm output voltage and lower bridge in adjusting
The difference of arm output voltage meets formulaIt is v to make mixed type MMC exchange side output voltagej；
In formula, vjMixed type MMC exchange side output voltages during for brownout operation, after mixed type MMC establishes DC voltage,
The quantity for adjusting full-bridge submodule and the conducting of half-bridge submodule again changes the above difference of bridge arm output voltage and lower bridge arm output voltage,
It realizes and adjusts mixing MMC exchange side output voltages, realize that it is v to adjust mixed type MMC exchange side output voltagejSo that mixed type
MMC can adjust the reactive power exchanged to AC network in transmitting active power, ensure the safety and stability of AC network
Operation.
In embodiment provided by the invention, after step (4), following steps are further included：If DC side output voltage is small
In or equal to exchange side output voltage amplitude, then inject low frequency circulation to bridge arm on mixed type MMC and lower bridge arm, otherwise, not to
Bridge arm and lower bridge arm injection low frequency circulation on mixed type MMC.If it is defeated to be more than exchange side for DC side output voltage after brownout operation
Go out voltage magnitude, half-bridge submodule well can be pressed at this time, not need to inject low frequency circulation into bridge arm again；If decompression fortune
DC side output voltage is less than or equal to exchange side output voltage amplitude after row, with the raising of transimission power, bridge arm current meeting
Become single direction, that is, be always just or be always negative, half-bridge submodule is caused persistently to charge or continuous discharge, can not be pressed,
It needs to inject low frequency circulation in bridge arm at this time, changes the direction of bridge arm current by force by injecting low frequency circulation, it is made to have just
There is negative, solution half-bridge submodule voltage-sharing, improve the active power conveying capacity of mixed type MMC.
The method for implanting of low frequency circulation is common-mode voltage injection method in embodiment provided by the invention, i.e., by upper and lower bridge
Corresponding common-mode voltage component is superimposed in arm equivalent voltage source output voltage reference value, the voltage is made to pass through bridge arm reactor,
Corresponding electric current is generated in bridge arm, realizes the injection of bridge arm low frequency circulation.
The frequency for injecting low frequency circulation is 15Hz~25Hz, and half-bridge submodule can be made to have the sufficient time to press, and is made
Press effect best.
After low frequency circulation is injected, upper bridge arm current is represented by：
Lower bridge arm electric current is represented by：
In formula, IjpFor upper bridge arm current, P is the active power of mixed type MMC outputs, and Q is the idle of mixed type MMC outputs
Power, VsmFor exchange side voltage magnitude, w is mains frequency, ψjFor bridge arm current phase, t is the time, V'dcAfter brownout operation
Mixed type MMC DC side output voltages, IcTo inject low frequency circulation amplitude, IjnFor lower bridge arm electric current, j=a, b, c, and a, b,
C represents A, B, C phases.
Must assure that all bridge arm currents after injection low frequency circulation has just and has negative, that is, needs to meet following formula：
After injecting circulation, it is desirable that all bridge arm currents must not exceed the through-flow energy of maximum of bridge arm switching device, it is desirable that meet
Following formula：
In formula, IlimMaximum current capacity for switching tube in bridge arm.
It needs to meet by the above-mentioned low frequency circulation amplitude size that must inject：
The present invention provides emulation embodiment, i.e., by HVDC system of the software emulation based on mixed type MMC, in mixed type
In the HVDC systems of MMC, the number of bridge arm full-bridge submodule and half-bridge submodule ratio is 1 in every phase:1, it is 10, capacitance
Voltage ratio is 1:1, it is 1kV, the number of full-bridge submodule and half-bridge submodule ratio is 1 in every phase lower bridge arm:1, be
10, capacitance voltage ratio is 1:1, it is 1kV.DC side rated voltage V during normal operationdc0=20kV, exchange side line electricity
It presses as 10kV, transmission rated active power is 20MW, rated reactive power 4MVar.
Emulation embodiment one
After brownout operation, DC voltage requires to become 15kV, and the active power of transmission is 15MW, and reactive power is transported in decompression
6MVar is adjusted to by 4MVar during row.As shown in figure 3, pass through the full-bridge submodule be connected in the upper bridge arm of change and lower bridge arm
With the quantity of half-bridge submodule, the sum of bridge arm output voltage and lower bridge arm output voltage in change change mixed type MMC outputs
DC voltage, DC voltage drops to 15kV by 20kV in Fig. 4 (a), then by changing upper bridge arm again with being connected in lower bridge arm
Full-bridge submodule and half-bridge submodule quantity so that the difference of upper bridge arm output voltage and lower bridge arm output voltage is kept not
Become so that mixed type MMC exchange side output voltages do not change, i.e. do not have shown in alternating current such as Fig. 4 (b) of mixed type MMC outputs
It changes, illustrates that mixed type MMC exchange side output voltages are controllable, as shown in Fig. 4 (d), transimission power becomes 15MW by 20MW, such as
Shown in Fig. 4 (c), after transimission power reduces, ac-side current becomes smaller, as shown in Fig. 4 (e), to the reactive power of power grid offer
Also it is flexibly controllable, 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 become 5kV, and transmission reactive power remains unchanged, reactive power 4MVar,
The active power of transmission is reduced to 5MW.Pass through the full-bridge submodule that is connected in the upper bridge arm of change and lower bridge arm and half-bridge submodule
Quantity, the sum of bridge arm output voltage and lower bridge arm output voltage in change change mixed type MMC DC side output voltages, by
20kV becomes 5kV, and pressure drop is larger at this time, by changing the full-bridge submodule be connected in upper bridge arm and lower bridge arm and half-bridge again
The quantity of module so that the difference of upper bridge arm output voltage and lower bridge arm output voltage is constant, makes mixed type MMC exchange side output electricity
Pressure remains unchanged, and such as Fig. 5 (a), active-power P becomes 5MW from 20MW, and reactive power remains unchanged, as shown in Fig. 5 (d), due to
DC voltage pressure drop is larger so that bridge arm current is always negative, and the full-bridge submodule as shown in Fig. 5 (b) can keep good equal
Pressure, but half-bridge submodule due to continuous discharge, can not be pressed, half-bridge submodule capacitor voltage is caused persistently to subtract as shown in Fig. 5 (c)
It is small so that mixed type MMC can not long-play, influence the stability of system.
Emulation embodiment three
After brownout operation, DC voltage requires to become 5kV, and transmission reactive power remains unchanged, reactive power 4MVar,
The active power of transmission is 5MW.Pass through the full-bridge submodule and the number of half-bridge submodule be connected in the upper bridge arm of change and lower bridge arm
It measures, the sum of bridge arm output voltage and lower bridge arm output voltage in change change mixed type MMC DC side output voltages, by 20kV
Become 5kV, by the quantity for changing the full-bridge submodule be connected in upper bridge arm and lower bridge arm and half-bridge submodule again so that on
The difference of bridge arm output voltage and lower bridge arm output voltage remains unchanged, and remains unchanged mixed type MMC exchange side output voltages, such as
Fig. 6 (a), active-power P become 5MW from 20MW, and reactive power remains unchanged, and make bridge arm by injecting low frequency circulation in bridge arm
Electric current changes direction, and as shown in Fig. 6 (d), even if larger in DC voltage pressure drop, bridge arm current is due to the injection of low frequency circulation
Becoming to have just is having negative, and the full-bridge submodule as shown in Fig. 6 (b) can still keep well pressing, while the half-bridge as shown in Fig. 6 (c)
Submodule also well can be pressed, and mixed type MMC can keep safe operation, ensure the stability of system.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, all any modification, equivalent and improvement made all within the spirits and principles of the present invention etc., should all include
Within protection scope of the present invention.
Claims (4)
1. a kind of brownout operation method of the HVDC systems based on mixed type MMC, the upper bridge arm of the mixed type MMC is comprising multiple
Full-bridge submodule and multiple half-bridge submodules, lower bridge arm includes multiple full-bridge submodules and multiple half-bridge submodules, feature exist
In including the following steps：
(1) DC voltage level V ' that straight-flow system must drop to is determined according to external environmentdc；
(2) active power transmitted and reactive power is needed to determine mixed type MMC exchange side output voltages according to during brownout operation
vj；
(3) quantity is connected by controlling full-bridge submodule and half-bridge submodule, bridge arm output voltage and lower bridge arm export in adjustings
The sum of voltage meets formula vnj+vpj=V 'dc, it is V ' to make mixed type MMC DC sides output voltagedc,
(4) quantity is connected by controlling full-bridge submodule and half-bridge submodule, bridge arm output voltage and lower bridge arm export in adjustings
Difference in voltage meets formulaIt is v to make mixed type MMC exchange side output voltagej；
(5) if V 'dc≤Vjm, then low frequency circulation is injected into the upper bridge arm and lower bridge arm of mixed type MMC, otherwise, not to mixed type
Low frequency circulation is injected in the upper bridge arm and lower bridge arm of MMC；
In formula, V 'dcMixed type MMC DC side output voltages, v during for brownout operationjMixed type MMC exchange side during for brownout operation
Output voltage, vpjTo connect the upper bridge arm output voltage of alternating current j phases, v in mixed type MMCnjIt is handed over to be connected in mixed type MMC
The lower bridge arm output voltage of galvanic electricity j phases, VjmMixed type MMC exchange side output voltage amplitudes during for brownout operation, j=a, b, c, and
A, b, c represent A, B, C phases.
2. the brownout operation method according to claim 1, which is characterized in that by being exported in upper and lower bridge arm equivalent voltage source
Corresponding common-mode voltage component is superimposed in voltage reference value, injects upper bridge arm from low frequency circulation to mixed type MMC and lower bridge arm.
3. the brownout operation method according to claim 1, which is characterized in that the frequency of the low frequency circulation for 15Hz~
25Hz。
4. the brownout operation method according to claim 1, which is characterized in that the size of the low frequency circulation is
In formula, active power of the P for mixed type MMC outputs, reactive powers of the Q for mixed type MMC outputs, VsmFor exchange side voltage
Amplitude, ICFor the amplitude of low frequency circulation, V 'dcFor the mixed type MMC DC side output voltages after brownout operation, IlimFor all bridges
The maximum current capacity of switching tube in arm.
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| 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 |
| 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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