CN106712054B - A kind of STATCOM device inhibiting capacitance voltage pulsation based on modular multilevel - Google Patents
A kind of STATCOM device inhibiting capacitance voltage pulsation based on modular multilevel Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
- H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
- H02J3/1842—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
- H02J3/1857—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters wherein such bridge converter is a multilevel converter
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/10—Flexible AC transmission systems [FACTS]
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Abstract
The present invention provides a kind of STATCOM device for inhibiting capacitance voltage pulsation based on modular multilevel, including directly by connection inductance in parallel in the STATCOM system of common node, the STATCOM system includes bridge arm phase A, bridge arm phase B, bridge arm phase C and bridge arm phase D；The present invention is based on MMC topologys, but eliminate the DC bus-bar voltage of MMC, eliminate the hidden danger of DC side common bus short circuit, improve the safety of device；The low frequency pulsating of the upper and lower bridge arm capacitance voltage of bridge arm phase is inhibited to reduce system cost to facilitate using smaller submodule capacitor and reduce device volume using low pressure low capacity capacitor；By buffer inductance alternative switch device bridge arm phase, capacitor and switching device number are reduced to the 3/4 of conventional structure, so that significant reducing apparatus cost and volume, reduce system loss；And the application of phase bridge arm of the invention is not limited solely to the application of reactive compensation, can substitute the existing phase bridge arm using the more level topology apparatus of cascaded H-bridges.
Description
Technical field
The present invention relates to power electronics flexible transmission equipment technical fields, and in particular to one kind is pressed down based on modular multilevel
The STATCOM device of capacitance voltage pulsation processed.
Background technique
The presence of a large amount of uneven industrial loads and single-phase large capacity load such as industrial ac arc furnace, electric railway,
And power electronic equipment is widely used, and brings a large amount of reactive current and negative-sequence current to electric system, not only increases
Loss, and endanger power equipment.In this context, since power electronic technique can participate in maintaining power system stability fortune
The distribution of capable and trend, the important technical for having become electric system compensation and adjusting.
Static synchronous compensator (Static Synchronous Compensator:STATCOM) is power electronic equipment
Participate in one of the main application that power grid is adjusted.STATCOM is seen as a controllable independent voltage source, can be into depending on application
Row reactive power compensation, the adjusting of access point voltage, harmonics restraint etc. are improved with improving the power quality of public access point (PCC)
The stability of system.As user steps up power quality requirement, STATCOM starts to receive more and more attention
And research.
Based on the STATCOM system of traditional two level PWM working methods, is limited and can not be answered by single power device pressure resistance
Mesohigh field is used, is limited by individual devices switching frequency, output end generally requires bulky passive filter ability
Access power grid.And modular multilevel is the technology that high-power transformation is realized with low voltage power devices, its modularization is set
Meter, using low tension switch device, output waveform be high-quality etc., that many merits are considered being very suitable to apply is high-power in middle high-pressure
Power quality regulation occasion.The basic principle is that connected using multiple mutually isostructural basic transformation device units, realize etc.
The staircase output voltage of number level is applied successfully in industrial circle to approach sinusoidal voltage waveform.
STATCOM based on modular multilevel (referred to as " MMC ") has been obtained in academia widely to be paid close attention to and grinds
Study carefully, and a kind of Transformerless STATCOM topological structure based on MMC of Authorization Notice No. CN201774259U, and is based on module
Reactive compensation (MMC-STATCOM) method for changing Multilevel Inverters is to provide in 105226687 A of CN in application notification number
A kind of energy-storage system topological structure and its control strategy suitable for large-scale photovoltaic power generation, which includes connected benefit
Repay device and A, B, C three phase network circuit；The compensation device is the dress for combining STATCOM function with energy-storage system function
It sets.The topological structure is easy to extend to high-power field, simultaneously because its switching frequency is low, loss is small, with energy storage device
In conjunction with can reduce the capacity of energy-storage system, to reduce the cost and volume of device.But based on modular multilevel
STATCOM needs boundary's concern and gives to solve there are still some intrinsic problems, firstly, public direct-current in the STATCOM based on MMC
There are the high voltages of power grid grade for bus, once dc-side short-circuit, will cause huge short circuit current, and burn device；Secondly, work
Journey experience have shown that, a large amount of submodule capacitor occupies the big quantity space of device in MMC, to increase the volume of device, together
When also increase system cost, the capacitance for reducing submodule capacitor can reduce significantly the capacitor of capacitor, to significantly subtract
The volume of few device, reducing apparatus cost；In addition, when the unbalanced system that STATCOM is used to have neutral dot system, and need
When repaying out-of-balance current, additional zero sequence channel makes one bridge arm of increase of MMC, the also proportional increasing of the cost and volume of device
Add.
Summary of the invention
In view of this, the present invention is directed to the STATCOMM system based on MMC, to reduce MMC submodule capacitor volume, eliminating
High voltage direct current side voltage, added number of devices when reducing compensation out-of-balance current, the present invention provides a kind of new idle
Compensation device, the present invention mutually eliminate DC bus-bar voltage using new bridge arm, pass through and increase connection capacitor between upper and lower bridge arm
Come the low frequency pulsating for forming energy channel to inhibit submodule capacitor voltage, using the buffer inductance and one of two low-voltage-grades
A passive resonant circuit constitutes zero-sequence current channel.
In order to solve the above technical problems, the technical solution used in the present invention is:
A kind of STATCOM device inhibiting capacitance voltage pulsation based on modular multilevel, including directly pass through connection electricity
Sense is connected in parallel on the STATCOM system of common node, and the STATCOM system includes bridge arm phase A, bridge arm phase B, bridge arm phase C and bridge
Arm phase D；
The bridge arm phase A, bridge arm phase B, bridge arm phase C are made of switching device, are connected respectively with A, B, C of power grid, shape
At the compensation channel of reactive current and negative-sequence current,
The bridge arm phase D is made of two inductance, is connect with the neutral point of power grid, and zero sequence current compensation channel is formed, with
Realize the total current compensation under power grid or laod unbalance.
The STATCOM system, the reactive current compensated needed for being calculated according to ip-iq method, negative-sequence current and zero sequence electricity
The instruction value of stream, then calculate MMC and export transducer port voltage corresponding to compensation electric current by instruction current, using phase-shifting carrier wave
The required port output voltage of modulation strategy synthesis.
The DC side of the STATCOM system does not include energy storage Support Capacitor.
The bridge arm phase A, the bridge arm phase B in the STATCOM system is identical with the structure of the bridge arm phase C, and
Bridge arm phase A, bridge arm phase B and bridge arm phase C are composed in series by upper bridge arm and lower bridge arm；
By multiple half-bridge submodules, successively series connection forms upper/lower terminal mouth circuit, the lower bridge arm to the upper bridge arm from beginning to end
It is identical with the structure of the upper bridge arm, and the lower port of the lower bridge arm connects the lower port of the upper bridge arm and collectively constitutes one
Bridge arm phase, that is, the structure rotation 180 degree of the upper bridge arm is as lower bridge arm and upper bridge arm drop-over.
The upper bridge arm and lower bridge arm separately include 2N submodule.
The tie point both sides of the upper bridge arm and lower bridge arm are respectively connected an identical buffer inductance.
For the half-bridge submodule by two full control switching device series connection, two terminal circuits formed after series connection are in parallel with capacitor,
Two full control switching devices distinguish one diode of inverse parallel.
The bridge arm phase D is connected by two buffer inductances and forms two-port circuit, buffer inductance and bridge arm phase A, bridge arm phase
B, the buffer inductance in bridge arm phase C is identical.
The bridge arm phase A, bridge arm phase B, bridge arm phase C, bridge arm one end phase D are another by positive common DC bus P connection
One end passes through negative common DC bus N connection.
The bridge arm phase A, bridge arm phase B, bridge arm phase C midpoint exit connect with power grid, as compensation electric current channel,
The midpoint of bridge arm phase D is connect by a communication channel with neutral point of electric network.
The communication channel is made of passive element.
Potential difference between the common DC bus P and common DC bus N of the STATCOM system is zero, described
The principle that potential difference in STATCOM system between common DC bus P and common DC bus N is zero is as follows:
The upper bridge arm and lower bridge arm resultant voltage of each bridge arm phase indicate are as follows:
Wherein, VCFor the sum of all submodule capacitor voltages of a bridge arm, ω0It is power frequency angular frequency,
Then the voltage of common DC bus P and N is uPN:
uPN=uU+uL=0 (3)
Wherein, uU、uLThe resultant voltage of respectively upper bridge arm and lower bridge arm.
The bridge arm is divided into upper and lower two sub- bridge arms, and every sub- bridge arm includes N submodule, the upper bridge of bridge arm phase
Upper and lower sub- bridge arm midpoint and the upper and lower sub- bridge arm midpoint of lower bridge arm form energy channel by connection capacitance connection in arm.
The connection capacitor is subjected only to high frequency voltage, is not subject to the DC voltage and power-frequency voltage of power grid grade, that is, voltage
Grade and capacity are smaller.
The pulsation that the bridge arm of the connection capacitor is mutually able to achieve submodule capacitor voltage inhibits, and inhibits principle as follows:
The equivalent circuit of one bridge arm phase as shown in Fig. 2, omit power frequency ingredient and flip-flop, bridge arm phase it is equivalent
Circuit equivalent is Fig. 3, in Fig. 3, only retains the amount of active power of capable of generating, then Fig. 3 is further simplified as Fig. 4, in Fig. 4
Voltage, the electric current of high fdrequency component are expressed as
uU1=ue+Uh cos(ωt)
uU2=-ue-Uh cos(ωt)
uL1=-ue+Uh cos(ωt)
uL2=+ue-Uh cos(ωt)
(4)
Wherein, uU1It is the upper sub- bridge arm resultant voltage of upper bridge arm, uU2It is the lower sub- bridge arm resultant voltage of upper bridge arm；
uL1It is the upper sub- bridge arm resultant voltage of lower bridge arm, uL2It is the lower sub- bridge arm resultant voltage of lower bridge arm；ueIt is ihSwash
It encourages, ueFor high frequency content, angular frequency ω.
4 sub- bridge arm currents of each bridge arm phase are
iU1=Ih cos(ωt)
iU2=-Ih cos(ωt)
iL1=-Ih cos(ωt)
iL2=Ih cos(ωt)
(5)
Wherein, iU1It is the electric current of the upper sub- bridge arm of upper bridge arm, iU2It is the electric current of the lower sub- bridge arm of upper bridge arm；
iL1It is the electric current of the upper sub- bridge arm of lower bridge arm, iL2It is the electric current of the lower sub- bridge arm of lower bridge arm.
The then power of each sub- bridge arm are as follows:
First three items in every formula are of ac, do not generate active, last Xiang Weiyou term of works of every formula, also, upper bridge arm
It is active active contrary with lower bridge arm, to inhibit low frequency pulsating power contrary in upper and lower bridge arm capacitor.
The ihIt is a controlled freedom degree, controls ihAmplitude and phase to controlling upper and lower bridge arm Power Exchange
Direction and size.
The beneficial effect that the present invention reaches is:
1. the present invention is based on MMC topologys, but eliminate the DC bus-bar voltage of MMC, it is short to eliminate DC side common bus
The hidden danger on road, improves the safety of device, and remains the modularization feature of MMC.
2. engineering is practical to be proved, a large amount of floating capacitance occupies the huge space of device in MMC device, and cost is also very
To its corresponding half-bridge module is higher than, the present invention is directly reduced by the inhibition to a leading pulsating volage ingredient is accounted for
The voltage class that floating capacitance is born reduces system cost, reduces apparatus body convenient for selecting lesser floating capacitance
Product；
3. therefore the grid level voltages that the new bridge arm phase structure of the present invention eliminates both ends are able to use by switching device
The bridge arm of composition mutually substitutes the conventional bridge arm phase being made of switching device, and capacitor and switching device number are reduced to the 3/ of conventional structure
4, to significantly reduce installation cost and volume, in addition, it is conventional 3/4 that the driving circuit of device is also accordingly less, improve
The reliability of system, decreases system loss；
4. in the suppressing method of capacitance voltage low frequency pulsating, increased hardware component is almost minimum, and suppressing method is to compensation
Electric current is without influence；
5. the application of phase bridge arm of the invention is not limited solely to that the application of reactive compensation, existing use can be substituted
The phase bridge arm of the more level topology apparatus of cascaded H-bridges, such as cascaded H-bridges star topology, cascaded H-bridges star topology, preposition rectification circuit
Deng.
Detailed description of the invention
Present invention will be further explained below with reference to the attached drawings and examples.
Fig. 1 is STATCOM system proposed by the present invention；
Fig. 2 is single-phase fully equivalent circuit diagram of the invention；
Fig. 3 is the single-phase high frequency component equivalent circuit diagram of omission power frequency and flip-flop of the invention；
Fig. 4 is further to omit on the basis of Fig. 3 and be formed by single-phase active high frequency division after active unrelated ingredient
Measure equivalent circuit diagram；
In figure:
1 represents the upper bridge arm of each bridge arm phase；2 represent the lower bridge arm of each bridge arm phase；
Represent bridge arm on the son of each bridge arm；4 represent the sub- lower bridge arm of each bridge arm；
5 bridge arm buffer inductances；
The connection capacitor of 6 upper and lower bridge arms；
Connection inductance between 7 converters and power grid.
Specific embodiment
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
Attached drawing 1-4, the technical solution of the embodiment of the present invention is clearly and completely described.Obviously, described embodiment is this
A part of the embodiment of invention, instead of all the embodiments.Based on described the embodiment of the present invention, the common skill in this field
Art personnel every other embodiment obtained, shall fall within the protection scope of the present invention.
Embodiment
A kind of STATCOM system for inhibiting capacitance voltage pulsation based on modular multilevel, the STATCOM system are straight
Connection inductance in parallel was connected in common node, is not necessarily to transformer, which includes 4 bridge arm phases, wherein bridge arm
Phase A, bridge arm phase B, bridge arm phase C are made of switching device, and bridge arm phase D is made of two inductance.
The bridge arm phase A, bridge arm phase B, the structure of bridge arm phase C are identical, and each bridge arm is mutually by upper bridge arm 1, lower bridge arm 2 two
Bridge arm is composed in series, and upper bridge arm is successively connected from beginning to end by multiple half-bridge submodules, formed upper/lower terminal mouth circuit, lower bridge arm and
The structure of upper bridge arm is identical, is used as lower bridge arm after upper bridge arm two-port circuit rotation 180 degree, then with upper bridge arm drop-over, forms
The new bridge arm phase of the present invention, this is different from conventional MMC structure；The both sides of upper and lower bridge arm tie point respectively connect one it is identical slow
Rush inductance 5.Each bridge arm includes 2N submodule, and each half-bridge submodule is connected by two full control switching devices, shape after series connection
At two terminal circuits it is in parallel with capacitor, two full control switching devices distinguish one diode of inverse parallel.
Bridge arm phase D forms two-port circuit by two series connection of buffer inductance 5.
The bridge arm phase A, bridge arm phase B, bridge arm phase C and bridge arm one end phase D are connected by positive common DC bus P, it
The other end pass through negative common DC bus N connection；Bridge arm phase A, the midpoint of bridge arm phase B, bridge arm phase C, as exit,
It connects respectively one and connects A, B, C phase being connected to the grid after inductance 7, for compensating reactive current, the negative-sequence current of power grid；Bridge arm
The exit at the midpoint D hinders DC circuit (preferably LC industrial frequency resonance circuit) by one passive logical exchange of series connection, is connected to the grid
Neutral point, to form zero sequence current compensation channel.
Upper and lower bridge arm forms energy channel by connection capacitor 6, to inhibit low frequency arteries and veins in upper and lower bridge arm submodule capacitor
Dynamic, specific connection method is: bridge arm is divided into upper and lower two sub- bridge arms, and every sub- bridge arm includes N number of submodule, bridge arm phase
Sub- bridge arm midpoint passes through connection capacitance connection above and below for the upper and lower sub- bridge arm midpoint of upper bridge arm and lower bridge arm.The connection capacitance
And voltage class is smaller, according to requirement of engineering, can use single capacitor, and the cascade string of multiple capacitor compositions also can be used.
The calculation method and the prior art of the STATCOM system balance instruction are without essence difference.
In addition, bridge arm of the invention mutually can substitute the bridge arm phase of the more level of existing cascaded H-bridges, to reach only with half
Bridge submodule only synthesizes the purpose of output AC voltage.
As another embodiment of the invention, the common DC bus P and public direct-current of the STATCOM system are female
Potential difference between line N is zero, and the potential difference in the STATCOM system between common DC bus P and common DC bus N is zero
Principle it is as follows:
The upper bridge arm and lower bridge arm resultant voltage of each bridge arm phase indicate are as follows:
Wherein, VCFor the sum of all submodule capacitor voltages of a bridge arm, ω0It is power frequency angular frequency,
Then the voltage of common DC bus P and N is uPN:
uPN=uU+uL=0 (3)
Wherein, uU、uLThe resultant voltage of respectively upper bridge arm and lower bridge arm.
The bridge arm is divided into upper and lower two sub- bridge arms, and every sub- bridge arm includes N number of submodule, the upper bridge of bridge arm phase
Upper and lower sub- bridge arm midpoint and the upper and lower sub- bridge arm midpoint of lower bridge arm form energy channel by connection capacitance connection in arm.
The connection capacitor is subjected only to high frequency voltage, is not subject to the DC voltage and power-frequency voltage of power grid grade, that is, voltage
Grade and capacity are smaller.
The pulsation that the bridge arm of the connection capacitor is mutually able to achieve submodule capacitor voltage inhibits, and inhibits principle as follows:
The equivalent circuit of one bridge arm phase as shown in Fig. 2, omit power frequency ingredient and flip-flop, bridge arm phase it is equivalent
Circuit equivalent is Fig. 3, in Fig. 3, only retains the amount of active power of capable of generating, then Fig. 3 is further simplified as Fig. 4, in Fig. 4
Voltage, the electric current of high fdrequency component are expressed as
uU1=ue+Uh cos(ωt)
uU2=-ue-Uh cos(ωt)
uL1=-ue+Uh cos(ωt)
uL2=+ue-Uh cos(ωt)
(4)
Wherein, uU1It is the upper sub- bridge arm resultant voltage of upper bridge arm, uU2It is the lower sub- bridge arm resultant voltage of upper bridge arm；
uL1It is the upper sub- bridge arm resultant voltage of lower bridge arm, uL2It is the lower sub- bridge arm resultant voltage of lower bridge arm；ueIt is ihSwash
It encourages, ueFor high frequency content, angular frequency ω.
4 sub- bridge arm currents of each bridge arm phase are
iU1=Ih cos(ωt)
iU2=-Ih cos(ωt)
iL1=-Ih cos(ωt)
iL2=Ih cos(ωt)
(5)
Wherein, iU1It is the electric current of the upper sub- bridge arm of upper bridge arm, iU2It is the electric current of the lower sub- bridge arm of upper bridge arm；
iL1It is the electric current of the upper sub- bridge arm of lower bridge arm, iL2It is the electric current of the lower sub- bridge arm of lower bridge arm.
The then power of each sub- bridge arm are as follows:
First three items in every formula are of ac, do not generate active, last Xiang Weiyou term of works of every formula, also, upper bridge arm
It is active active contrary with lower bridge arm, to inhibit low frequency pulsating power contrary in upper and lower bridge arm capacitor.
The ihIt is a controlled freedom degree, controls ihAmplitude and phase to controlling upper and lower bridge arm Power Exchange
Direction and size.
The beneficial effect that the present invention reaches is:
1. the present invention is based on MMC topologys, but eliminate the DC bus-bar voltage of MMC, it is short to eliminate DC side common bus
The hidden danger on road, improves the safety of device, and remains the modularization feature of MMC.
2. engineering is practical to be proved, a large amount of floating capacitance occupies the huge space of device in MMC device, and cost is also very
To its corresponding half-bridge module is higher than, the present invention is directly reduced by the inhibition to a leading pulsating volage ingredient is accounted for
The voltage class that floating capacitance is born reduces system cost, reduces apparatus body convenient for selecting lesser floating capacitance
Product；
3. therefore the grid level voltages that the new bridge arm phase structure of the present invention eliminates both ends are able to use by switching device
The bridge arm of composition mutually substitutes the conventional bridge arm phase being made of switching device, and capacitor and switching device number are reduced to the 3/ of conventional structure
4, to significantly reduce installation cost and volume, in addition, it is conventional 3/4 that the driving circuit of device is also accordingly less, improve
The reliability of system, decreases system loss；
4. in the suppressing method of capacitance voltage low frequency pulsating, increased hardware component is almost minimum, and suppressing method is to compensation
Electric current is without influence；
5. the application of phase bridge arm of the invention is not limited solely to that the application of reactive compensation, existing use can be substituted
The phase bridge arm of the more level topology apparatus of cascaded H-bridges, such as cascaded H-bridges star topology, cascaded H-bridges star topology, preposition rectification circuit
Deng.
The embodiment that embodiment described above, the only present invention are applied to STATCOM, those skilled in the art should be able to manage
Solution, half-bridge submodule of the present invention belong to preferred structure of the invention, and the present invention is not limited to the bridge being made of half-bridge circuit
Arm also includes other more level or various forms of single level monopole type construction modules, is related to the topological structure of such phase bridge arm
It should all cover in the present invention.
Claims (5)
1. a kind of STATCOM device for inhibiting capacitance voltage pulsation based on modular multilevel, it is characterised in that: including directly logical
Connection inductance in parallel is crossed in the STATCOM system of common node, the STATCOM system includes bridge arm phase A, bridge arm phase B, bridge arm
Phase C and bridge arm phase D；
The bridge arm phase A, bridge arm phase B, bridge arm phase C are made of switching device, are connected respectively with A, B, C of power grid, and nothing is formed
The compensation channel of function electric current and negative-sequence current；
The bridge arm phase D is made of two inductance, is connect with the neutral point of power grid, and zero sequence current compensation channel is formed, to realize
Total current compensation under power grid or laod unbalance；
The bridge arm phase A, the bridge arm phase B in the STATCOM system is identical with the structure of the bridge arm phase C, and bridge arm
Phase A, bridge arm phase B and bridge arm phase C are composed in series by upper bridge arm and lower bridge arm；
By multiple half-bridge submodules, successively series connection forms upper/lower terminal mouth circuit, the lower bridge arm and institute to the upper bridge arm from beginning to end
The structure for stating bridge arm is identical, and the lower port of the lower bridge arm connects the lower port of the upper bridge arm and collectively constitutes a bridge arm
Phase, that is, the structure rotation 180 degree of the upper bridge arm is as lower bridge arm and upper bridge arm drop-over；
The upper bridge arm and lower bridge arm separately include 2N submodule, and N is nonnegative integer；The connection of the upper bridge arm and lower bridge arm
It respectively connects an identical buffer inductance on point both sides；
The bridge arm phase A, bridge arm phase B, bridge arm phase C, bridge arm one end phase D pass through positive common DC bus P connection, the other end
Pass through negative common DC bus N connection；The bridge arm phase A, bridge arm phase B, bridge arm phase C midpoint exit connect with power grid,
As the channel of compensation electric current, the midpoint of bridge arm phase D is connect by a communication channel with neutral point of electric network；The communication channel
It is made of passive element；
Potential difference between the common DC bus P and common DC bus N of the STATCOM system is zero；Each bridge arm phase
Upper bridge arm and lower bridge arm resultant voltage indicate are as follows:
Wherein, VCFor the sum of all submodule capacitor voltages of a bridge arm, ω0It is power frequency angular frequency,
Then the voltage of common DC bus P and N is uPN:
uPN=uU+uL=0 (3)
Wherein, uU、uLThe resultant voltage of respectively upper bridge arm and lower bridge arm；
The bridge arm is divided into upper and lower two sub- bridge arms, and every sub- bridge arm includes N number of submodule, in the upper bridge arm of bridge arm phase
Upper and lower sub- bridge arm midpoint and the upper and lower sub- bridge arm midpoint of lower bridge arm form energy channel by connection capacitance connection；
The STATCOM system, reactive current, negative-sequence current and the zero-sequence current compensated needed for being calculated according to ip-iq method
Instruction value, then calculate MMC and export transducer port voltage corresponding to compensation electric current by instruction current, it is modulated using phase-shifting carrier wave
The required port output voltage of strategy synthesis.
2. inhibiting the STATCOM device of capacitance voltage pulsation based on modular multilevel as described in claim 1, feature exists
In: the DC side of the STATCOM system does not include energy storage Support Capacitor.
3. inhibiting the STATCOM device of capacitance voltage pulsation based on modular multilevel as described in claim 1, feature exists
In: the half-bridge submodule is connected by two full control switching devices, and two terminal circuits formed after series connection are in parallel with capacitor, and two are complete
It controls switching device and distinguishes one diode of inverse parallel.
4. inhibiting the STATCOM device of capacitance voltage pulsation based on modular multilevel as described in claim 1, feature exists
In: the bridge arm phase D is connected by two buffer inductances and forms two-port circuit, buffer inductance and bridge arm phase A, bridge arm phase B, bridge arm
Buffer inductance in phase C is identical.
5. inhibiting the STATCOM device of capacitance voltage pulsation based on modular multilevel as described in claim 1, feature exists
In: voltage, the electric current of high fdrequency component are expressed as
uU1=ue+Uhcos(ωt)
uU2=-ue-Uhcos(ωt)
uL1=-ue+Uhcos(ωt)
uL2=+ue-Uhcos(ωt) (4)
Wherein, uU1It is the upper sub- bridge arm resultant voltage of upper bridge arm, uU2It is the lower sub- bridge arm resultant voltage of upper bridge arm；
uL1It is the upper sub- bridge arm resultant voltage of lower bridge arm, uL2It is the lower sub- bridge arm resultant voltage of lower bridge arm；ueIt is ihExcitation, ue
For high frequency content, angular frequency ω；
4 sub- bridge arm currents of each bridge arm phase are
iU1=Ihcos(ωt)
iU2=-Ihcos(ωt)
iL1=-Ihcos(ωt)
iL2=Ihcos(ωt) (5)
Wherein, iU1It is the electric current of the upper sub- bridge arm of upper bridge arm, iU2It is the electric current of the lower sub- bridge arm of upper bridge arm；iL1It is lower bridge arm
The electric current of upper sub- bridge arm, iL2It is the electric current of the lower sub- bridge arm of lower bridge arm；
The then power of each sub- bridge arm are as follows:
The ihIt is a controlled freedom degree, controls ihAmplitude and phase to control the direction of upper and lower bridge arm Power Exchange
And size.
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