CN105305843A - Three-phase series half H-bridge modular multilevel DC converter and control method thereof - Google Patents
Three-phase series half H-bridge modular multilevel DC converter and control method thereof Download PDFInfo
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- CN105305843A CN105305843A CN201510673038.XA CN201510673038A CN105305843A CN 105305843 A CN105305843 A CN 105305843A CN 201510673038 A CN201510673038 A CN 201510673038A CN 105305843 A CN105305843 A CN 105305843A
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Abstract
The invention relates to a three-phase series half H-bridge modular multilevel DC converter and a control method thereof. The three-phase series half H-bridge modular multilevel DC converter comprises 3m series single-phase half H-bridge MMCs (Modular Multilevel Converters) and 3m single-phase transformers connected with the 3m series single-phase half H-bridge MMCs respectively, wherein m is a positive integer. According to the invention, the single-phase half H-bridge MMCs are connected in series at a direct current side, the number of switching components is only one third of that of a traditional MMC under the premise of bearing the same DC voltage and adopting the same switching components, and the fabrication cost is lower. Under the condition of bearing the same DC voltage and adopting the same switching components, the capacity of the modular multilevel DC converter provided by the invention is one third of that of the traditional MMC, thereby greatly reducing the construction threshold of an MMC station, and being more extensive in application occasion.
Description
Technical field
The present invention relates to a kind of three-phase series half H bridge type modular multilevel DC converter and control method thereof, belong to field of power electronics.
Background technology
Voltage source converter (VoltageSourceConverter, VSC) has active reactive independent regulation, can power to passive network, trend reversion without the need to changing the advantages such as polarity of voltage, be particularly suitable as the drop point converter in direct current network.The modularization multi-level converter (ModularMultilevelConverter, MMC) occurred in recent years is the up-to-date member in voltage source converter VSC family, also belongs to voltage source converter VSC.Compared with the topology of or three-level voltage source type converter VSC flat with traditional two, modularization multi-level converter MMC has the following advantages: output voltage waveforms harmonic content is little; Loss is little, and its switching frequency is only the 2-3 of fundamental frequency doubly; There are good packaging effects and autgmentability etc.At technology and aspect of performance, the modularization multi-level converter MMC drop point converter that be more suitable as direct current network more topological than traditional voltage source converter VSC.
The topological structure of traditional modularization multi-level converter MMC as shown in Figure 1, it is by multiple semi-bridge type module (HalfBridgeSub-Module, or bridge-type module (FullBridgeSub-Module HBSM), or clamp Shuangzi module (ClampDoubleSub-Module FBSM), CDSM) brachium pontis of three-phase bridge is composed in series, during normal operation, module capacitance voltage U
c=U
dc/ N, wherein, U
dcfor direct voltage, N is the number of modules in a brachium pontis.The modularization multi-level converter MMC of whole parallel three phase needs 6N module altogether.High cost is the major defect of modularization multi-level converter MMC.Use the switching component number of the modularization multi-level converter MMC of half-bridge module HBSM to be the twice of traditional electrical potential source type converter VSC, use the switching device number of the modularization multi-level converter MMC of full-bridge modules FBSM to be then four times of traditional electrical potential source type converter VSC.Because renewable energy source distribution disperses, capacity is generally less, and the converter capacity of access direct current network is also less.If the parallel three phase converter of routine is used as direct current network drop point converter, three groups of brachium pontis all bear whole direct voltage, no matter drop point amount of capacity, and the electric pressure of direct current network converter is identical, and cost is also close to identical, inadvisable economically.
Summary of the invention
For the deficiencies in the prior art, the invention provides a kind of three-phase series half H bridge type modular multilevel DC converter;
Present invention also offers the control method of above-mentioned three-phase series half H bridge type modular multilevel DC converter;
Terminological interpretation:
1, nearest level approach method, see Guan Minyuan, Xu Zheng, etc. level approaches the principal wave harmonic wave characteristic analytical Calculation [J] of modulation recently. high voltage technique, 2010,36 (5): 1327-1332.
2, sinusoidal carrier stacking method, see M.Saeedifard, R.Iravani, Dynamicperformanceofamodularmultilevelback-to-backHVDCsy stem [J], IEEETransactionsonPowerDelivery, vol.25, no.4, pp.2903-2912, Oct.2010.
Technical scheme of the present invention is:
A kind of three-phase series half H bridge type modular multilevel DC converter, 3m the single-phase transformer that the single-phase half H bridge type MMC comprising 3m series connection and the single-phase half H bridge type MMC connected with 3m is respectively connected, m is positive integer; Described single-phase half H bridge type MMC comprises: upper SM brachium pontis, lower SM brachium pontis, the first inductance, the second inductance, the first electric capacity, the second electric capacity, described upper SM brachium pontis, described first inductance, described second inductance, described lower SM brachium pontis connect successively and with described first electric capacity of connecting and described second Capacitance parallel connection, first inductance is identical with the second inductance, and the first electric capacity is identical with the second electric capacity; Described upper SM brachium pontis and described lower SM brachium pontis include the SM module of several series connection, and the number of the SM module that described upper SM brachium pontis and described lower SM brachium pontis comprise is identical; One end of the secondary side of described single-phase transformer connects described first inductance and described second inductance respectively, the other end of the secondary side of described single-phase transformer connects described first electric capacity and described second electric capacity respectively, in a described 3m single-phase transformer, every 3 single-phase transformers are one group, and 3 single-phase transformer primary sides in same group adopt delta connection or the wiring of star isolated neutral.
Set identical with the SM module used in Fig. 1, in Fig. 1, the voltage of each SM module is U
c=U
dc/ N, wherein, U
dcrefer to direct voltage, and in the present invention, the number of modules n=(U on single-phase half H bridge type MMC in SM brachium pontis or lower SM brachium pontis
dc/ 3)/U
c=N/3, as m=1, the present invention has 3 upper SM brachium pontis and 3 lower SM brachium pontis, total 2N SM number of modules.Compared with modularization multi-level converter MMC traditional in Fig. 1, bearing in identical direct voltage situation, number of modules reduces to 2N by 6N, switching component decreased number 2/3rds, thus reaches the object reduced costs.
In the present invention, upper SM brachium pontis, lower SM brachium pontis, the first inductance, the second inductance, the first electric capacity, the second electric capacity constitute a H bridge type loop, provide alternating current circulation path; Alternating current is divided equally in the lower loop that the upper loop of upper SM brachium pontis, the first electric capacity composition and lower SM brachium pontis, the second electric capacity form.
The primary side of described single-phase transformer adopts triangle or star isolated neutral wiring isolation zero-sequence current.
Preferred according to the present invention, described SM module is semi-bridge type module HBSM, bridge-type module FBSM or clamp Shuangzi module CDSM.
The control method of above-mentioned three-phase series half H bridge type modular multilevel DC converter, concrete steps comprise:
(1) in setting, the reference voltage of SM brachium pontis is:
the reference voltage of the lower SM brachium pontis of setting is:
u
reffor the reference voltage of converter, U
dfor the DC voltage of converter;
(2) approach modulation method or sinusoidal carrier stacking method by nearest level and obtain the SM number of modules that the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis need conducting;
(3) to the capacitance voltage sequence of all SM modules in the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis, if the sense of current is the electric capacity flowing into SM module, be the capacitor charging of SM module, then select the SM module conducting that the capacitance voltage of SM module is minimum; If the sense of current is the electric capacity of SM module, be the capacitor discharge of SM module, then select the SM module conducting that the capacitance voltage of SM module is the highest.
Beneficial effect of the present invention is:
1, single-phase half H bridge type MMC connects in DC side by the present invention, and under the prerequisite of bearing identical direct voltage and employing same switch components and parts, switching device number of the present invention only has 1/3rd of traditional modularization multi-level converter MMC, and cost is lower.
2, when bearing identical direct voltage and employing same switch components and parts, capacity of the present invention is 1/3rd of traditional modularization multi-level converter MMC, and greatly reduce the construction threshold of MMC current conversion station, application scenario is more extensive.
Accompanying drawing explanation
Fig. 1 is the topology diagram of traditional modularization multi-level converter MMC;
Fig. 2 is topology diagram of the present invention;
Fig. 3 is the topology diagram of semi-bridge type module HBSM of the present invention;
Fig. 4 is the topology diagram of bridge-type module FBSM of the present invention;
Fig. 5 is the topology diagram of clamp Shuangzi module CDSM of the present invention;
Fig. 6 is equivalent circuit diagram of the present invention;
Fig. 7 is equivalent circuit current circulation figure of the present invention;
Fig. 8 is the equivalent circuit diagram after the present invention simplifies;
In Fig. 1-Fig. 8, L
0be the first inductance value and the second inductance value, C is the first capacitance and the second capacitance, u
areffor the alternating voltage that single-phase half H bridge type MMC exports, u
afor single-phase transformer secondary side voltage.
Embodiment
Below in conjunction with Figure of description and embodiment, the present invention is further qualified, but is not limited thereto.
Embodiment 1
A kind of three-phase series half H bridge type modular multilevel DC converter, 3 single-phase transformers that the single-phase half H bridge type MMC comprising 3 series connection and the single-phase half H bridge type MMC connected with 3 is respectively connected; Described single-phase half H bridge type MMC comprises: upper SM brachium pontis, lower SM brachium pontis, the first inductance, the second inductance, the first electric capacity, the second electric capacity, described upper SM brachium pontis, described first inductance, described second inductance, described lower SM brachium pontis connect successively and with described first electric capacity of connecting and described second Capacitance parallel connection, first inductance is identical with the second inductance, and the first electric capacity is identical with the second electric capacity; Described upper SM brachium pontis and described lower SM brachium pontis include the SM module of several series connection, i.e. SM1 module, SM2 module in Fig. 2 ... SMn module, the number of the SM module that described upper SM brachium pontis and described lower SM brachium pontis comprise is identical; One end of the secondary side of described single-phase transformer connects described first inductance and described second inductance respectively, the other end of the secondary side of described single-phase transformer connects described first electric capacity and described second electric capacity respectively, and the primary side of the single-phase transformer of 3 adopts delta connection.As shown in Figure 2.
Set identical with the SM module used in Fig. 1, in Fig. 1, the voltage of each SM module is U
c=U
dc/ N, wherein, U
dcrefer to direct voltage, and in the present invention, the number of modules n=(U on single-phase half H bridge type MMC in SM brachium pontis or lower SM brachium pontis
dc/ 3)/U
c=N/3, the present invention has 3 upper SM brachium pontis and 3 lower SM brachium pontis, total 2N SM number of modules.Compared with modularization multi-level converter MMC traditional in Fig. 1, bearing in identical direct voltage situation, number of modules reduces to 2N by 6N, switching component decreased number 2/3rds, thus reaches the object reduced costs.
In the present invention, upper SM brachium pontis, lower SM brachium pontis, the first inductance, the second inductance, the first electric capacity, the second electric capacity constitute a H bridge type loop, provide alternating current circulation path; Alternating current is divided equally in the lower loop that the upper loop of upper SM brachium pontis, the first electric capacity composition and lower SM brachium pontis, the second electric capacity form.
Described SM module is semi-bridge type module HBSM, bridge-type module FBSM or clamp Shuangzi module CDSM.The topology diagram of semi-bridge type module HBSM, bridge-type module FBSM or clamp Shuangzi module CDSM is respectively as shown in Fig. 3, Fig. 4, Fig. 5.
The equivalent circuit diagram of three-phase series half H bridge type modular multilevel DC converter described in the present embodiment as shown in Figure 6; In Fig. 6, the reference voltage of upper SM brachium pontis is:
the reference voltage of lower SM brachium pontis is:
u
reffor the reference voltage of converter, U
dfor the DC voltage of converter;
The equivalent circuit current circulation of three-phase series half H bridge type modular multilevel DC converter described in the present embodiment is schemed as shown in Figure 7: direct current only flows through the upper SM brachium pontis of converter and lower SM brachium pontis, does not flow through the first electric capacity and the second electric capacity.Alternating current by upper SM brachium pontis, first electric capacity composition upper loop and lower SM brachium pontis, second electric capacity composition lower loop divide equally, each electric current is expressed as;
I
1for upper SM bridge arm current, i
2for lower SM bridge arm current, i
c1be the charging current of the first electric capacity, i
c2be the charging current of the second electric capacity, I
dfor direct current, i
afor alternating current.
The final equivalent electric circuit of three-phase series half H bridge type modular multilevel DC converter described in the present embodiment is as shown in Figure 8: equivalent inductance
l
0be the first inductance and the second inductance value, C is the first electric capacity and the second capacitance, and ω=2 π f, f are mains frequency, f=50Hz..
Embodiment 2
The control method of the three-phase series half H bridge type modular multilevel DC converter described in embodiment 1, concrete steps comprise:
(1) in setting, the reference voltage of SM brachium pontis is:
the reference voltage of the lower SM brachium pontis of setting is:
u
reffor the reference voltage of converter, U
dfor the DC voltage of converter;
(2) approach modulation method or sinusoidal carrier stacking method by nearest level and obtain the SM number of modules that the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis need conducting;
(3) to the capacitance voltage sequence of all SM modules in the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis, if the sense of current is the electric capacity flowing into SM module, be the capacitor charging of SM module, then select the SM module conducting that the capacitance voltage of SM module is minimum; If the sense of current is the electric capacity of SM module, be the capacitor discharge of SM module, then select the SM module conducting that the capacitance voltage of SM module is the highest.
Claims (3)
1. a three-phase series half H bridge type modular multilevel DC converter, is characterized in that, 3m the single-phase transformer that the single-phase half H bridge type MMC comprising 3m series connection and the single-phase half H bridge type MMC connected with 3m is respectively connected, and m is positive integer; Described single-phase half H bridge type MMC comprises: upper SM brachium pontis, lower SM brachium pontis, the first inductance, the second inductance, the first electric capacity, the second electric capacity, described upper SM brachium pontis, described first inductance, described second inductance, described lower SM brachium pontis connect successively and with described first electric capacity of connecting and described second Capacitance parallel connection, first inductance is identical with the second inductance, and the first electric capacity is identical with the second electric capacity; Described upper SM brachium pontis and described lower SM brachium pontis include the SM module of several series connection, and the number of the SM module that described upper SM brachium pontis and described lower SM brachium pontis comprise is identical; One end of the secondary side of described single-phase transformer connects described first inductance and described second inductance respectively, the other end of the secondary side of described single-phase transformer connects described first electric capacity and described second electric capacity respectively, in a described 3m single-phase transformer, every 3 single-phase transformers are one group, and 3 single-phase transformer primary sides in same group adopt delta connection or the wiring of star isolated neutral.
2. a kind of three-phase series half H bridge type modular multilevel DC converter according to claim 1, it is characterized in that, described SM module is semi-bridge type module HBSM, bridge-type module FBSM or clamp Shuangzi module CDSM.
3. the control method of the three-phase series half H bridge type modular multilevel DC converter described in claim 1 or 2, it is characterized in that, concrete steps comprise:
(1) in setting, the reference voltage of SM brachium pontis is:
the reference voltage of the lower SM brachium pontis of setting is:
u
reffor the reference voltage of converter, U
dfor the DC voltage of converter;
(2) approach modulation method or sinusoidal carrier stacking method by nearest level and obtain the SM number of modules that the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis need conducting;
(3) to the capacitance voltage sequence of all SM modules in the upper SM brachium pontis of each single-phase half H bridge type MMC and lower SM brachium pontis, if the sense of current is the electric capacity flowing into SM module, be the capacitor charging of SM module, then select the SM module conducting that the capacitance voltage of SM module is minimum; If the sense of current is the electric capacity of SM module, be the capacitor discharge of SM module, then select the SM module conducting that the capacitance voltage of SM module is the highest.
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| US10715065B2 (en) | 2016-12-15 | 2020-07-14 | General Electric Company | Power conversion systems and associated methods |
| CN112468009A (en) * | 2020-11-12 | 2021-03-09 | 东南大学 | MMC converter topological structure |
| CN112910291A (en) * | 2019-11-19 | 2021-06-04 | 北京金风科创风电设备有限公司 | Converter control method, controller and control equipment and converter system |
| CN112928943A (en) * | 2021-01-28 | 2021-06-08 | 东南大学 | Direct current side series connection alternating current side parallel connection type electric energy tapping device |
| CN113054861A (en) * | 2021-03-08 | 2021-06-29 | 东南大学 | Series MMC converter topological structure with few modules |
| CN113872459A (en) * | 2021-09-22 | 2021-12-31 | 国网江苏省电力有限公司扬州供电分公司 | Serial MMC topological structure and control method |
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| CN105720844A (en) * | 2016-04-22 | 2016-06-29 | 西安交通大学 | Novel three-phase serial modular multilevel converter HVDC converter |
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| CN112928943A (en) * | 2021-01-28 | 2021-06-08 | 东南大学 | Direct current side series connection alternating current side parallel connection type electric energy tapping device |
| CN113054861A (en) * | 2021-03-08 | 2021-06-29 | 东南大学 | Series MMC converter topological structure with few modules |
| WO2022188255A1 (en) * | 2021-03-08 | 2022-09-15 | 东南大学 | Topology structure for series-connected mmc converters with small number of modules |
| US11909214B2 (en) | 2021-03-08 | 2024-02-20 | Southeast University | Topology of series-connected MMC with a small number of modules |
| CN113872459A (en) * | 2021-09-22 | 2021-12-31 | 国网江苏省电力有限公司扬州供电分公司 | Serial MMC topological structure and control method |
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