CN103199725A - MMC (modular multilevel converter) circular current restrain strategy based on parallel resonance - Google Patents

MMC (modular multilevel converter) circular current restrain strategy based on parallel resonance Download PDF

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CN103199725A
CN103199725A CN2013101510793A CN201310151079A CN103199725A CN 103199725 A CN103199725 A CN 103199725A CN 2013101510793 A CN2013101510793 A CN 2013101510793A CN 201310151079 A CN201310151079 A CN 201310151079A CN 103199725 A CN103199725 A CN 103199725A
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circuit
mmc
inductance
current
circulation
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梅军
郑建勇
杜晓舟
吉宇
韩少华
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Southeast University
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Southeast University
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Abstract

The invention discloses an MMC (modular multilevel converter) circular current restrain circuit based on parallel resonance. Aiming at the characteristic that main component in an MMC bridge arm circular current is second harmonic, the series connection of an LC parallel circuit and an inductor is adopted to replace an original current-limiting inductance, and the resonant frequency of the LC parallel circuit is twice of a fundamental frequency, so that the second harmonic component in the bridge arm current can not normally circulate, thereby effectively achieving the restrain effect on the second circular current.

Description

A kind of MMC circulation based on parallel resonance suppresses strategy
Technical field
The present invention relates to power electronics in the application on power system field, relate in particular to a kind of circulation inhibition method of modularization multi-level converter.
Background technology
Modularization multi-level converter (MMC) is a kind of novel voltage with multiple levels translation circuit, and it is by the mode with a plurality of submodule cascades, and the very high voltage of output can superpose.Be compared to traditional many level topological structure, change topological structure and have characteristics such as output harmonic wave is few, degree of modularity height, thereby in electric power system, be with a wide range of applications.
With respect to many level current transformers in the past, MMC has many advantages, but has also brought some new problems simultaneously.Wherein one of sixty-four dollar question is exactly to produce circulation between upper and lower bridge arm, thereby the operation of current transformer is exerted an influence.The appearance of the circulation in the current transformer can cause that output waveform distorts, degradation problem under the brachium pontis loss increase, the stability of a system.The generation of circulation on the brachium pontis, so long as since the dividing potential drop effect of the fluctuation of MMC neutron module capacitance voltage and brachium pontis upper flow inductance produce.For the composition of circulation, there has been a lot of scholars to do a lot of relevant researchs both at home and abroad, and confirmed that the main component in the circulation is second harmonic, accounted for more than 90% of circulation composition.Therefore, for the inhibition of circulation, mainly be exactly the inhibition to second harmonic component in the circulation.
Aspect the inhibition of circulation, also there is a lot of articles to introduce the achievement of this respect at present.But these articles mainly all are aimed at the design and research of circulation controller aspect, these designs are partial to the compensation to modulating wave, mainly be to realize by software algorithm, realize that more complicated, reaction speed are slower, and can cause the robust performance of system to descend.On the method that suppresses circulation, suppress circulation by changing main circuit topology, also namely use the method for hardware to suppress circulation, be a kind of more efficiently selection.But current achievement in research about this respect does not but almost have.
Therefore, invent and a kind ofly come circulation in the inhibition system based on the method that changes the current transformer main circuit topological structure, just seem particularly important.
Summary of the invention
The objective of the invention is in order to solve the inhibition problem of the circulation in the MMC structure, the present invention starts with from changing main circuit topological structure, by at brachium pontis series connection secondary resonant circuit, thereby has well realized inhibition for secondary circulation.The use of this scheme only used inductance and electric capacity, realization convenient, stability of a system height, cost are also comparatively cheap.This method does not need to change modulation and control circuit, is compared to the method for traditional use controller, and this method has that response speed is fast, robust performance is strong and characteristics such as inhibition is good.
For realizing this purpose, the present invention solves by following technical proposals:
The circulation inhibition method of modularization multi-level converter of the present invention, its characteristics are, use the series connection of inductance and LC parallel circuits, thereby have solved the problem that circulation suppresses in hardware circuit.This circulation inhibitor mainly comprises two parts, namely is connected on inductance and LC resonant circuit on the brachium pontis.
The every of MMC uses two LC resonant circuits mutually, and they are connected on respectively on the upper and lower brachium pontis of MMC, replaces in traditional MMC converter circuit the position of original current-limiting inductance on the brachium pontis.In the outside of shunt circuit at inductor of series connection, the equivalent reactance of circuit when being used for adjusting first-harmonic and flowing through.By L1 and the C in the adjustment resonant circuit, and the inductor L2 of series connection, just can realize the flexible to circuit parameter.By above three variablees are regulated, make after this circuit replaces original current-limiting inductance: when first-harmonic flow through this circuit, the equivalent reactance of circuit equated with the value of original current-limiting inductance; When second harmonic flow through this circuit, resonance took place in the LC shunt circuit, thereby is equivalent to very big resistance sense, and then the circulation of restriction second harmonic.
Description of drawings
Fig. 1 is the traditional MMC structure chart when not adopting the circulation inhibitor;
Fig. 2 is the MMC structure chart when adopting this scheme;
Fig. 3 is the circulation suppressor circuit schematic diagram when adopting this scheme;
Fig. 4 is the circulation comparison of wave shape figure that adopts these scheme front and back.
Specific embodiments
Below in conjunction with accompanying drawing technical scheme of the present invention is described in further detail.
)Used after the circulation inhibition method of introducing among the present invention the MMC circuit structure as shown in Figure 2.Compare with original MMC circuit shown in Figure 1, just can find that the modification to circuit topology of this scheme has mainly changed original current-limiting inductance L0 on the brachium pontis in traditional MMC converter circuit into circuit shown in Figure 3 exactly.Because the main component of circulation is second harmonic component, so by adjusting the LC shunt circuit, make it that parallel resonance take place, can suppress the second harmonic that flows through on the brachium pontis effectively when second harmonic is flowed through.The circuit diagram of this scheme as shown in Figure 3, A, B are connected in series to two tie points (it is positive direction that power taking stream flows to B by A) on the brachium pontis for this circulation suppresses circuit, C and L1 constitute antiresonant circuit, L2 is series inductance.By calculating, keep it when first-harmonic flows through, the equivalent reactance of circuit is L0, when second harmonic flow through, resonance took place in the LC loop.C wherein, L1, L2 are variable.If fundamental frequency is f, then the selection of parameter need be satisfied following equation:
Figure 2013101510793100002DEST_PATH_IMAGE001
(1)
Figure 441010DEST_PATH_IMAGE002
(2)
Wherein, ,
Figure 736994DEST_PATH_IMAGE004
,
In this case, can obtain in the brachium pontis electric current N time (
Figure 209563DEST_PATH_IMAGE006
) equiva lent impedance expression formula when electric current flows through this circulation and suppresses circuit:
(3)
Wherein Behind the abbreviation, obtain
Figure DEST_PATH_IMAGE009
(4)
(1) formula is brought in (4), and cancellation C obtains
(5)
Work as N=0 as can be known by (5) formula, 1,2 o'clock, when the electric current that also namely flows through this circuit was respectively direct current, fundamental current and secondary current, equiva lent impedance was respectively
Figure DEST_PATH_IMAGE011
(6)
Figure 347918DEST_PATH_IMAGE012
(7)
Figure DEST_PATH_IMAGE013
(8)
Through type (6) (7) (8) as can be known, under perfect condition, (namely ignore resistance all in the circuit), this circuit is for almost not influence of the DC component in the brachium pontis electric current, and identical with the effect of original current-limiting inductance L0 for the influence of fundametal compoment, secondary current then can't circulate.Therefore, this circuit can be in not influencing the brachium pontis electric current suppresses secondary current component wherein under the situation of direct current and the normal circulation of fundametal compoment effectively.
Fig. 4 has shown the MATLAB simulation waveform comparison diagram that uses before and after this scheme, and wherein A is for using the circulation waveform before this circulation suppresses scheme, and B is the circulation waveform that has used after the scheme among the present invention.Can find that by contrast the brachium pontis circulation among the MMC has obtained effective control.
The above only is preferred implementation of the present invention; be noted that for those skilled in the art; under the prerequisite that does not break away from the principle of the invention, can also make the some improvements and modifications that can expect, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (1)

1. the circulation inhibition method based on the modularization multi-level converter MMC of parallel resonance is characterized in that: two antiresonant circuits of series connection on the brachium pontis of described MMC; Wherein, described antiresonant circuit comprises two inductance and a capacitor, with one of them inductance formation in parallel with capacitor LC loop; The back of connecting with the another one inductance, this shunt circuit is constituted described antiresonant circuit; Again two these antiresonant circuits are connected on the upper and lower brachium pontis;
Component parameters in the described antiresonant circuit meets the following conditions: establish in traditional MMC converter circuit that original current-limiting inductance is L0 on the brachium pontis, this circulation suppresses circuit and is made of two inductance L 1, L2 and capacitor C, and fundamental frequency is f, then:
Figure 325796DEST_PATH_IMAGE001
(1)
Figure 610147DEST_PATH_IMAGE002
(2)
Wherein,
Figure 960357DEST_PATH_IMAGE003
,
Figure 988356DEST_PATH_IMAGE004
,
Figure 169939DEST_PATH_IMAGE005
, X represents impedance, is satisfying under the situation of above-mentioned formula, can obtain in the brachium pontis electric current N time ( ) equiva lent impedance expression formula when electric current flows through this antiresonant circuit:
Figure 197117DEST_PATH_IMAGE007
(3)
Wherein , abbreviation obtains
(4)
As seen, be fundamental frequency in the frequency of this circuital current of flowing through, namely during N=1, the value of the current limiting reactor in the equiva lent impedance of this circuit and the traditional MMC circuit is suitable; Power frequency at this circuit of flowing through is the twice of fundamental frequency, namely during N=2, and this circuit generation parallel resonance.
CN2013101510793A 2013-04-27 2013-04-27 MMC (modular multilevel converter) circular current restrain strategy based on parallel resonance Pending CN103199725A (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103929084A (en) * 2014-05-06 2014-07-16 湖南大学 Modular multilevel converter low-frequency control method based on resonant filter circuit
CN104617800A (en) * 2015-01-30 2015-05-13 天津大学 Improved redundancy type MMC current converter structure having direct-current fault current-limiting capacity
CN105140906A (en) * 2015-07-30 2015-12-09 特变电工新疆新能源股份有限公司 Modular multilever converter (MMC) module topological structure applicable for flexible direct current transmission
CN105305405A (en) * 2015-09-29 2016-02-03 特变电工新疆新能源股份有限公司 MMC module topology applied to MMC type flexible DC power transmission
CN106411167A (en) * 2016-11-25 2017-02-15 东南大学 MMC circulation inhibition system and method based on self-redundancy state prediction
CN107248730A (en) * 2017-08-14 2017-10-13 广东电网有限责任公司电力科学研究院 The short-circuit protection circuit of flexible direct current power transmission system
CN112310993A (en) * 2019-08-02 2021-02-02 全球能源互联网研究院有限公司 Hybrid converter topology structure for forced current conversion and control method thereof
CN113572170A (en) * 2021-08-16 2021-10-29 北京荣信慧科科技有限公司 High-frequency oscillation suppression method of flexible direct current converter
WO2024110007A1 (en) * 2022-11-21 2024-05-30 Hitachi Energy Ltd Modular multi-level converter for dc transmission

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011000428A1 (en) * 2009-07-02 2011-01-06 Abb Technology Ag Power converter with multi-level voltage output and harmonics compensator
CN102224669A (en) * 2008-11-21 2011-10-19 Abb技术有限公司 Power converter with multi-level voltage output and harmonics filter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102224669A (en) * 2008-11-21 2011-10-19 Abb技术有限公司 Power converter with multi-level voltage output and harmonics filter
WO2011000428A1 (en) * 2009-07-02 2011-01-06 Abb Technology Ag Power converter with multi-level voltage output and harmonics compensator

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103929084A (en) * 2014-05-06 2014-07-16 湖南大学 Modular multilevel converter low-frequency control method based on resonant filter circuit
CN104617800A (en) * 2015-01-30 2015-05-13 天津大学 Improved redundancy type MMC current converter structure having direct-current fault current-limiting capacity
CN105140906A (en) * 2015-07-30 2015-12-09 特变电工新疆新能源股份有限公司 Modular multilever converter (MMC) module topological structure applicable for flexible direct current transmission
CN105305405A (en) * 2015-09-29 2016-02-03 特变电工新疆新能源股份有限公司 MMC module topology applied to MMC type flexible DC power transmission
CN105305405B (en) * 2015-09-29 2018-01-16 特变电工新疆新能源股份有限公司 A kind of MMC module topologies applied to MMC type flexible DC power transmission
CN106411167A (en) * 2016-11-25 2017-02-15 东南大学 MMC circulation inhibition system and method based on self-redundancy state prediction
CN107248730A (en) * 2017-08-14 2017-10-13 广东电网有限责任公司电力科学研究院 The short-circuit protection circuit of flexible direct current power transmission system
CN112310993A (en) * 2019-08-02 2021-02-02 全球能源互联网研究院有限公司 Hybrid converter topology structure for forced current conversion and control method thereof
CN112310993B (en) * 2019-08-02 2024-04-19 国网智能电网研究院有限公司 Hybrid converter topology structure for forced commutation and control method thereof
CN113572170A (en) * 2021-08-16 2021-10-29 北京荣信慧科科技有限公司 High-frequency oscillation suppression method of flexible direct current converter
CN113572170B (en) * 2021-08-16 2024-04-05 北京荣信慧科科技有限公司 High-frequency oscillation suppression method for flexible direct current converter
WO2024110007A1 (en) * 2022-11-21 2024-05-30 Hitachi Energy Ltd Modular multi-level converter for dc transmission

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Application publication date: 20130710