CN107317497B - Improve the modulator approach of bridge-type Modular multilevel converter output level number - Google Patents
Improve the modulator approach of bridge-type Modular multilevel converter output level number Download PDFInfo
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- CN107317497B CN107317497B CN201710495960.3A CN201710495960A CN107317497B CN 107317497 B CN107317497 B CN 107317497B CN 201710495960 A CN201710495960 A CN 201710495960A CN 107317497 B CN107317497 B CN 107317497B
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- 230000001939 inductive effect Effects 0.000 abstract description 6
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Classifications
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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
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
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Abstract
The invention discloses a kind of raising bridge-type Modular multilevel converter (full bridge modular multilevel converter, abbreviation FBMMC) output level number modulator approach, every phase upper and lower bridge arm of FBMMC is all made of bridge-type full voltage submodule and bridge-type half voltage submodule, switching appropriate is carried out to both submodules, so that the exchange of FBMMC exchange output is surveyed level number and increased.The present invention improves exchange output level number, significantly improves the effect of nearest level approximatioss, significantly reduces the harmonic content of FBMMC output voltage.Moreover, the present invention not will lead to the problems such as submodule capacitor voltage offset, the fluctuation of bridge arm inductive drop spike, FBMMC DC voltage.
Description
[technical field]
The invention belongs to field of power electronics, are related to a kind of raising bridge-type Modular multilevel converter output level number
Modulator approach.
[background technique]
Modular multilevel converter has the circuit of high modularization, is easy to implement Integration Design, shortens project week
Phase, save the cost are with a wide range of applications.
In order to realize the more level outputs in exchange side, it is necessary to use specific modulator approach.Modular multilevel converter
Modulation system has critical influence to its performance.Current existing modulation technique is broadly divided into two classes: multi-carrier PWM modulation
Technology and nearest multilevel modulation technique.The higher PWM modulation technology of switching frequency, switch frequency are generallyd use when number of modules is lower
Rate is excessively high to mean that switching loss is excessive, and level modulation strategy can not only reduce the switch frequency of power electronic devices recently
Rate and switching loss, and realize that simple, dynamic response is very fast.If but using nearest multilevel modulation technique when level number is lower
Then output waveform harmonic content is high, and waveform is poor.
The document for improving nearest level modulation existing at present is as follows:
[1]Lin L,Lin Y,He Z,et al.Improved Nearest-Level Modulation for a
Modular Multilevel Converter With a Lower SubmoduleNumber[J].IEEE
Transactions on Power Electronics,2016,31(8):5369-5377.
[2]Hu P,Jiang D.A Level-Increased Nearest Level Modulation Method for
Modular Multilevel Converters[J].IEEE Transactions on Power Electronics,2015,
30(4):1836-1842.
Document [1] makes the modulation waveform phase of upper and lower bridge arm different in the case where not changing number of modules with [2] to mention
The method of the output level number of high modulation wave, but this method will lead to submodule voltage average value it is relatively low, and capacitance voltage wave
Move it is larger, bridge arm inductive drop fluctuation it is larger, DC bus-bar voltage fluctuate the problems such as.Therefore it needs more to be suitably modified measure
In the case where not influencing voltage fluctuation of capacitor to raising output level number.
[summary of the invention]
In view of the above-mentioned problems, the invention proposes a kind of raising bridge-type Modular multilevel converter output level numbers
Modulator approach improves output waveform quality by the improvement to topology and modulation strategy.
The invention adopts the following technical scheme:
A kind of modulator approach improving bridge-type Modular multilevel converter output level number, it is characterised in that: full-bridge
Every phase upper and lower bridge arm of type Modular multilevel converter is by N number of (N is even number) bridge-type full voltage submodule and 1 full-bridge
Type half voltage submodule composition, the bridge-type full voltage submodule and bridge-type half voltage submodule need the quantity of switching
It is calculated according to following methods:
WhenWhen for odd number, upper and lower bridge arm respectively puts into 1 bridge-type half voltage submodule, and need to put into is complete
The quantity of bridge type full voltage submodule is calculated according to the following formula and is obtained:
In formula,
Wherein, ndown indicates that lower bridge arm puts into bridge-type full voltage submodule quantity, and bridge arm puts into full-bridge in nup expression
Type full voltage submodule quantity, Us indicate the modulated signal of a phase, and Uc indicates the specified electricity of bridge-type full voltage submodule capacitor
Pressure, N indicate the number of bridge-type full voltage submodule in a bridge arm, and round () indicates bracket function；
Iarm indicates the bridge arm current, and uh indicates that the actual capacitance voltage of bridge-type half voltage submodule, uhref indicate complete
The capacitance voltage rated value of bridge type half voltage submodule,
WhenWhen for even number, bridge-type half voltage submodule, the bridge-type full voltage submodule of investment are not put into
Quantity is calculated according to the following formula and is obtained:
Further, whenWhen for odd number, work as ck=1, the operating mode of bridge-type half voltage submodule is
PLUS, i.e. forward conduction, work as ck=-1, and the operating mode of bridge-type half voltage submodule is MINUS, i.e. reverse-conducting.
Further, the bridge-type full voltage submodule and bridge-type half voltage submodule of the switching of every phase upper and lower bridge arm are calculated
Number when, first by modulated signal it is discrete be staircase waveform, the ladder height of staircase waveform isIt is calculated according to this staircase waveform every
The bridge-type full voltage submodule of the switching of phase upper and lower bridge arm and the number of bridge-type half voltage submodule, wherein Udc is direct current
Busbar voltage.
Further, full voltage submodule and half voltage submodule are all full bridge structure.
Further, the capacitor voltage rating of bridge-type full voltage submodule isThe capacitor of bridge-type half voltage submodule
Voltage rating is
Compared with prior art, the present invention at least has the advantages that the invention discloses a kind of raising bridge-types
The modulator approach of Modular multilevel converter output level number, every phase upper and lower bridge arm of FBMMC is all by bridge-type full voltage
Module and bridge-type half voltage submodule are constituted, and carry out switching appropriate to both submodules, so that FBMMC exchange output
Exchange is surveyed level number and is increased.The present invention improves exchange output level number, significantly improves the effect of nearest level approximatioss, significantly
Reduce the harmonic content of FBMMC output voltage.Moreover, the present invention not will lead to submodule capacitor voltage offset, bridge arm inductance
The problems such as due to voltage spikes, the fluctuation of FBMMC DC voltage.
[Detailed description of the invention]
Fig. 1 is new topological converter structure schematic diagram proposed by the present invention；
Fig. 2 is the topological structure of FBFVSM；
Fig. 3 is the topological structure of FBHVSM；
Fig. 4 is the modulation effect contrast simulation of new modulation strategy proposed by the present invention and the nearest level modulation strategy of tradition
Figure (with 4 FBFVSM, for 1 FBHVSM)；
Fig. 5 is to export a phase voltage waveform using traditional level modulation strategy FBMMC recently；
Fig. 6 is to export a phase voltage waveform using new type of modulation strategy FBMMC of the invention；
Fig. 7 is using the nearest level modulation strategy bridge arm inductive drop wave pattern of improvement in document [1]；
Fig. 8 is the bridge arm inductive drop wave pattern using modulator approach of the present invention；
Fig. 9 is the submodule capacitor voltage wave pattern using modulator approach of the present invention.
[specific embodiment]
A kind of raising bridge-type Modular multilevel converter (full bridgemodular multilevel
Converter, abbreviation FBMMC) output level number mixed topology modulator approach, every phase upper and lower bridge arm of FBMMC is all by N number of complete
Bridge type full voltage submodule (full bridge full voltage sub module, abbreviation FBFVSM) and 1 bridge-type half
Voltage submodule (full bridge half voltage sub module, abbreviation FBHVSM) is constituted, to both submodules
Switching appropriate is carried out, so that the ladder height of the staircase waveform of FBMMC exchange output becomes original half, to make FBMMC
Exchange side output level number improved by N+1 to 2N+1.The present invention not will lead to submodule capacitor voltage offset, bridge arm inductance electricity
The problems such as pointing peak, the fluctuation of FBMMC DC voltage.
The specific implementation steps are as follows by the present invention:
(1) upper and lower bridge arm is made of N number of FBFVSM and 1 FBHVSM；
(2) modulation strategy are as follows: modulated signal it is discrete be staircase waveform, the ladder height of staircase waveform isAccording to this ladder
Wave calculates the number of the FBFVSM and FBHVSM of the switching of every phase upper and lower bridge arm.FBFVSM is finally generated by balance of voltage strategy
With the trigger signal of FBHVSM, exported accordingly so that FBMMC be made to generate.Udc is DC bus-bar voltage.
Wherein, FBFVSM and FBHVSM is full bridge structure.The voltage rating of the capacitor of FBFVSM isThe electricity of FBHVSM
The voltage rating of appearance is
(concisely for statement, the detailed step for calculating the number of the FBFVSM and FBHVSM of the switching of every phase upper and lower bridge arm is
By taking a phase as an example):
(1) whenWhen for odd number, upper and lower bridge arm respectively puts into a FBHVSM, and (incidence of FBHVSM is by ck
Value determines), FBFVSM number of investment are as follows:
In formula,
Wherein, ndown indicates that lower bridge arm puts into FBFVSM quantity, and bridge arm puts into FBFVSM quantity in nup expression, and Us is indicated
The modulated signal of one phase, Uc indicate the voltage rating of FBFVSM capacitor, and N indicates the number of FBFVSM in a bridge arm, round
() indicates bracket function.
Work as ck=1, the operating mode of FBHVSM is PLUS, i.e. forward conduction, works as ck=-1, the operating mode of FBHVSM is
MINUS, i.e. reverse-conducting.Iarm indicates the bridge arm current.Uh indicates that the actual capacitance voltage of FBHVSM, uhref indicate
The capacitance voltage rated value of FBHVSM,
(2) whenWhen for even number, bridge-type half voltage submodule, the FBFVSM of upper and lower bridge arm investment are not put into
Quantity are as follows:
FBHVSM can be realized by way of increasing new module, in the case where topology is not easy change, can also be led to
Software set is crossed, original FBFVSM is set as FBHVSM, to realize this method.
The present invention not will lead to submodule capacitor voltage offset, the fluctuation of bridge arm inductive drop spike, FBMMC DC voltage
The problems such as.
It is concise for statement, below with a phase, for N=18.It is noted that the present invention is when three-phase or N take other even numbers,
It is all suitable for.
Fig. 1 is FBMMC inverter topology of the invention.Each bridge arm is made of N number of FBFVSM and 1 FBHVSM.
Fig. 2 and Fig. 3 is respectively the structure chart of FBFVSM and FBHVSM, and the capacitor voltage rating of FBHVSM is FBFVSM capacitor
The half of voltage rating.
Fig. 4 is the modulation principle comparison diagram of new modulation strategy proposed by the present invention and the nearest level modulation strategy of tradition
(by taking 4 FBFVSM as an example).
From the comparison of Fig. 5 and Fig. 6 as can be seen that the present invention increases the output level number of FBMMC, improve modulation effect,
Reduce output harmonic wave.
Fig. 7 and Fig. 8 is respectively the method for using document [1] and the bridge arm inductive drop wave of new type of modulation strategy of the invention
Shape figure.It can be seen that voltage fluctuation and due to voltage spikes on bridge arm inductance is obviously reduced in the present invention.
The present invention can make the capacitance voltage of FBFVSM and FBHVSM be stable in its rated value attached as can be seen from Figure 9
Closely.Demonstrate feasibility of the invention.
Claims (3)
1. a kind of modulator approach for improving bridge-type Modular multilevel converter output level number, it is characterised in that: bridge-type
Every phase upper and lower bridge arm of Modular multilevel converter is by N number of bridge-type full voltage submodule and 1 bridge-type half voltage
The capacitor voltage rating of module composition, bridge-type full voltage submodule isThe specified electricity of capacitor of bridge-type half voltage submodule
Pressure isUdc is DC bus-bar voltage, and N is even number, the bridge-type full voltage submodule and bridge-type half voltage submodule
Block needs the quantity of switching to be calculated according to following methods:
Modulated signal it is discrete be staircase waveform, the ladder height of staircase waveform isAccording to this staircase waveform, every phase upper and lower bridge arm is calculated
Switching bridge-type full voltage submodule and bridge-type half voltage submodule number:
WhenWhen for odd number, upper and lower bridge arm respectively puts into 1 bridge-type half voltage submodule, the bridge-type for needing to put into
The quantity of full voltage submodule is calculated according to the following formula and is obtained:
In formula,
Wherein, ndown indicates that lower bridge arm puts into bridge-type full voltage submodule quantity, and bridge arm investment bridge-type is complete in nup expression
Voltage submodule quantity, Us indicate the modulated signal of a phase, and Uc indicates the voltage rating of bridge-type full voltage submodule capacitor, N
Indicate the number of bridge-type full voltage submodule in a bridge arm, round () indicates bracket function；
Iarm indicates the bridge arm current, and uh indicates that the actual capacitance voltage of bridge-type half voltage submodule, uhref indicate bridge-type
The capacitance voltage rated value of half voltage submodule,
WhenWhen for even number, bridge-type half voltage submodule, the bridge-type full voltage submodule quantity of investment are not put into
It calculates and obtains according to the following formula:
2. a kind of modulation methods for improving bridge-type Modular multilevel converter output level number according to claim 1
Method, it is characterised in that: whenWhen for odd number, work as ck=1, the operating mode of bridge-type half voltage submodule is PLUS,
That is forward conduction, works as ck=-1, and the operating mode of bridge-type half voltage submodule is MINUS, i.e. reverse-conducting.
3. a kind of modulation methods for improving bridge-type Modular multilevel converter output level number according to claim 1
Method, it is characterised in that: calculate the bridge-type full voltage submodule and bridge-type half voltage submodule of the switching of every phase upper and lower bridge arm
Number when, first by modulated signal it is discrete be staircase waveform, the ladder height of staircase waveform isIt is calculated according to this staircase waveform every
The bridge-type full voltage submodule of the switching of phase upper and lower bridge arm and the number of bridge-type half voltage submodule.
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| CN111756264B (en) * | 2020-07-02 | 2023-06-06 | 华北电力大学（保定） | Nearest half-level approximation PWM (pulse-Width modulation) hybrid modulation method suitable for medium-voltage three-phase MMC (modular multilevel converter) |
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| CN103312208A (en) * | 2013-05-06 | 2013-09-18 | 浙江大学 | Zero-error recent level modulating method of modularized multi-level current converter |
| CN103633871B (en) * | 2013-11-20 | 2016-10-05 | 华南理工大学 | Mixed type multilevel converter based on full-bridge and half-bridge module and control method thereof |
| CN105186897B (en) * | 2015-08-20 | 2017-12-15 | 华中科技大学 | A kind of nearest level control method suitable for Modular multilevel converter rectifier |
| CN105391329B (en) * | 2015-12-11 | 2017-11-17 | 华中科技大学 | A kind of bridge-type MMC alternating voltages lift operation method |
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