CN105656023B - A kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter - Google Patents
A kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter Download PDFInfo
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- CN105656023B CN105656023B CN201510465370.7A CN201510465370A CN105656023B CN 105656023 B CN105656023 B CN 105656023B CN 201510465370 A CN201510465370 A CN 201510465370A CN 105656023 B CN105656023 B CN 105656023B
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Abstract
The invention discloses a kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter, by calculating under current time using the size of the capacitance voltage difference obtained by two kinds of different switching strategies, compared with the capacitance voltage threshold value of setting, when difference is more than the capacitance voltage threshold value of setting, the higher switching strategy of selecting switch frequency, when difference is less than the capacitance voltage threshold value of setting, the relatively low switching strategy of selecting switch frequency.Control signal obtained by the switching strategy of final choice is sent into valve body to be controlled.In this way, effectively IGBT switching frequency can be controlled by the setting of threshold value within 50 150Hz, greatly reduces the loss of switching tube.Capacitance voltage threshold value frequency reducing method flow chart is shown in Figure of description 2.
Description
Technical field
The present invention relates to power electronics and custom power field, and in particular to one kind is applied to modularization multi-level converter
Capacitance voltage threshold value frequency reducing method.
Background technology
（1）Relative to traditional flexible direct current power transmission system（Based on IGBT serial connection technologies）, changed based on modular multilevel
The flexible direct current power transmission system of device (modular multilevel converter, MMC) is flowed because its is simple in construction, is easy to
The features such as engineering construction, causes the extensive concern of domestic and international experts and scholars in recent years.
（2）At present, it is that the transverter damages compared to Traditional DC converter valve to restrict one of wide variety of principal elements of MMC
Consume larger, it is lost the main reason for big and is that MMC IGBT switching frequencies are higher, and with the raising of voltage class, son
Number of modules is significantly increased, and power consumption also can be bigger, influences the efficiency of current conversion station, it is therefore necessary to which research reduces the side of switching frequency
Method, to reduce the power consumption of current conversion station.
（3）In the research process of the frequency reducing technology for modularization multi-level converter, many researchers indicate
The method for reducing switching frequency, Guan Minyuan, Xu Zheng et al. have set one group of bound near submodule rated capacity voltage, will be equal
Pressure algorithm emphasis be put on the submodule for surmounting bound, by it is out-of-limit to those and last moment put into or cut off
The capacitance voltage of submodule, a holding factor is multiplied by, keeps the size of the factor can effective control submodule by adjusting
The switching time, so as to reduce switching frequency.Sun Shixian, Tian Jie et al. are changed to NLM modulation algorithms, its general principle
It is to subtract each other modulating wave and the number of modules that last moment is put into, when the absolute value of difference is more than setting value A（0≤A≤0.5）
When, the number of modules currently put into will change accordingly：Or be the integer higher than modulating wave, or be the integer less than modulating wave.
The good controlling switch frequency of rational control and regulation value A cans.The holding factor of first method is needed according to different works
Condition is done many experiments and just can determine that, and bad regulation, and second method is similar to SPWM, is typically all very high voltage in engineering
Grade, so NLM algorithms are enough.
（4）The present invention devises a kind of effective IGBT frequency reducing sides according to the relation of voltage fluctuation of capacitor and switching frequency
Method --- capacitance voltage threshold value frequency reducing method, this method can be by setting capacitance voltage threshold value to effectively reduce switching frequency, will
Switching frequency is controlled between 50-150Hz, greatly reduces the switching loss of submodule.
The content of the invention
（1）The invention provides a kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter, the drop
Frequency method is by judging the size of the difference of the capacitance voltage sum under synchronization obtained by two kinds of different switching strategies, if in threshold
The switching strategy of low frequency is then used within the scope of value, the switching strategy of high frequency is used if outside threshold range.So may be used
Effectively to reduce IGBT switching frequency, reach the low-loss purpose of drop.
（2）A kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter, the modular multilevel change
Stream device is made up of six bridge arms of three-phase, and each bridge arm is by coupling or non-coupled inductance and several identical submodules
Cascade is formed.Each submodule is by two IGBT, two backward diodeds and a DC capacitor composition, it is characterised in that institute
The capacitance threshold value frequency reducing method stated comprises the following steps：
1) a sub- module capacitance voltage threshold Δ u is set, whether the threshold value is used as carries out extra submodule switching behaviour
The index made.Size can by adjusting threshold value increases or reduced IGBT switching frequency.Modular multilevel changes
Stream device approaches modulation algorithm using nearest level.
2) when nearest level approaches the switching module number change that modulation algorithm provides, first using the submodule of low frequency
Switching strategy, the basic thought of the switching strategy are：The current switching module number that modulation algorithm obtains is approached according to nearest level
The switching module number obtained with last moment does subtraction, then puts into or cuts off according to the size of the sense of current and capacitance voltage
The submodule number of two moment differences.The state for preserving now input submodule is S1, and calculates and put into submodule under S1 states
Capacitance voltage value summation.
3) on the basis of S1 states, according to（2）The submodule switching strategy of description, additionally put into Nx submodule simultaneously
Nx submodule is cut off, to keep level number constant, Nx is the integer more than or equal to 1.Preserve the state for now putting into submodule
For S2, and calculate the capacitance voltage value summation that submodule is put under S2 states.
4) by two capacitance voltage value summations under S1 and S2 states subtract each other and divided by Nx.Take its absolute value and Δ u ratios
Compared with when more than Δ u, because capacitance voltage difference is larger, it is necessary to high frequency switching operation be carried out to reduce this difference, so choosing
State S2 is selected as final control signal；And when this absolute value is less than Δ u, submodule capacitor voltage value difference is not very
Greatly, it is not necessary to extra switching operation is carried out, so selection state S1 is as final control signal.
Brief description of the drawings
The flexible DC power transmission basic structure of figure one
The capacitance voltage threshold value frequency reducing method flow chart of figure two
After frequency reducing method of the figure three using the present invention, the voltage fluctuation of capacitor and IGBT switching frequencies of different threshold values
After frequency reducing method of the figure four using the present invention, the relativity of IGBT switching frequencies and voltage fluctuation of capacitor
Embodiment
（1）Below in conjunction with accompanying drawing and the embodiment of the example in detail present invention, but the present invention is not by the tool
Body example is limited.
（2）A kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter, the modular multilevel change
Stream device is made up of six bridge arms of three-phase, and each bridge arm is by coupling or non-coupled inductance and several identical submodules
Cascade is formed.Each submodule is by two IGBT, two backward diodeds and a DC capacitor composition, the structure such as institute of figure one
Show, DC current and upper and lower bridge arm current direction are as shown in the figure.
（3）A sub- module capacitance voltage threshold Δ u is set, whether the threshold value is used as carries out extra submodule switching operation
An index.Size can by adjusting threshold value increases or reduced IGBT switching frequency.Modulator approach is using nearest
Level approaches modulation algorithm.When nearest level approaches the switching module number change that modulation algorithm provides, first using low frequency
Submodule switching strategy, the tactful basic thought are：The current switching module that modulation algorithm obtains is approached according to nearest level
The switching module number that number obtains with last moment does subtraction, then puts into or cuts according to the size of the sense of current and capacitance voltage
Except the submodule number of two moment differences.The state for preserving now input submodule is S1, and calculates and put into submodule under S1 states
The capacitance voltage value summation of block.On the basis of S1 states, Nx submodule is additionally put into simultaneously according to submodule Switching rule
Nx submodule is cut off, to keep level number constant, Nx is the integer more than or equal to 1.Preserve the state for now putting into submodule
For S2, and calculate the capacitance voltage value summation that submodule is put under S2 states.
（4）By two capacitance voltage value summations under S1 and S2 states subtract each other and divided by Nx.Take its absolute value and Δ u ratios
Compared with when more than Δ u, because capacitance voltage difference is larger, it is necessary to high frequency switching operation be carried out to reduce this difference, so choosing
State S2 is selected as final control signal；And when this absolute value is less than Δ u, submodule capacitor voltage value difference is not very
Greatly, it is not necessary to extra switching operation is carried out, so selection state S1 is as final control signal.Particular flow sheet such as figure two
It is shown.
（5）It was found from figure three, capacitance voltage threshold value frequency reducing method is controlled by increasing capacitance voltage threshold value, successfully will be average
Switching frequency is controlled in below 150Hz, if capacitance voltage threshold value Δ u settings are sufficiently large, switching frequency is minimum to can reach 50Hz.
（6）Figure three is simplified to the graph of a relation of voltage fluctuation of capacitor value and switching frequency by figure four, it can be seen that with
Capacitance voltage threshold value Δ u increase, switching frequency is in reduction trend, and switching loss can also reduce accordingly, but submodule
The fluctuation of capacitance voltage value can become big accordingly.This can cause the change of circulation waveform, the change of converter valve output current wave
The problems such as, therefore capacitance voltage threshold value Δ u size is reasonably selected according to requirement of engineering.Compare rational system of selection
It is：Adjust capacitance voltage threshold value Δ u, while the fluctuation range of detection sub-module capacitance voltage value, when fluctuation range is close to engineering
During the maximum of allowed band, capacitance voltage threshold value Δ u now is most suitable value.
Claims (1)
1. a kind of capacitance voltage threshold value frequency reducing method applied to modularization multi-level converter, the modularization multi-level converter by
Six bridge arms of three-phase are formed, and each bridge arm is by coupling or non-coupled inductance and several identical sub-module cascade structures
Into；Each submodule is by two IGBT, two backward diodeds and a DC capacitor composition, it is characterised in that described electricity
Hold voltage threshold frequency reducing method to comprise the following steps：
(1) a sub- module capacitance voltage threshold Δ u is set, whether the threshold value is as carrying out extra submodule switching operation
One index；Size can by adjusting threshold value increases or reduced IGBT switching frequency；Modularization multi-level converter
Modulation algorithm is approached using nearest level；
(2) when nearest level approaches the switching module number change that modulation algorithm provides, first using the submodule switching of low frequency
Strategy, the basic thought of the switching strategy are：According to nearest level approach current switching module number that modulation algorithm obtains with it is upper
The switching module number that one moment obtained does subtraction, then puts into or cut off two according to the size of the sense of current and capacitance voltage
The submodule number of moment difference；The state for preserving now input submodule is S1, and calculates the electricity that submodule is put under S1 states
Hold magnitude of voltage summation；
(3) on the basis of S1 states, according to step（2）The submodule switching strategy of description, additionally put into Nx submodule simultaneously
Nx submodule is cut off, to keep level number constant, Nx is the integer more than or equal to 1；Preserve the state for now putting into submodule
For S2, and calculate the capacitance voltage value summation that submodule is put under S2 states；
(4) by two capacitance voltage value summations under S1 and S2 states subtract each other and divided by Nx；Its absolute value is taken compared with Δ u, when
During more than Δ u, because capacitance voltage difference is larger, it is necessary to high frequency switching operation be carried out to reduce this difference, so selection shape
State S2 is as final control signal；And when this absolute value is less than Δ u, submodule capacitor voltage value difference is not very greatly, no
Need to carry out extra switching operation, so selection state S1 is as final control signal.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103326622A (en) * | 2013-06-19 | 2013-09-25 | 国家电网公司 | Photovoltaic system suitable for high-voltage direct-current transmission |
| CN104135177A (en) * | 2014-07-24 | 2014-11-05 | 华北电力大学 | Voltage balancing control method applicable for sub-module capacitor voltage hierarchy of high-level MMC (Modular Multilevel Converter) |
| CN104218833A (en) * | 2014-05-26 | 2014-12-17 | 长沙理工大学 | Flexible voltage-sharing modulation method for capacitors of slave modules of modular multilevel converters |
| CN104269838A (en) * | 2013-09-24 | 2015-01-07 | 许继集团有限公司 | Valve level control method for flexible DC power transmission system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR101200554B1 (en) * | 2010-12-24 | 2012-11-13 | 한국에너지기술연구원 | Multi-phase interleaved bidirectional dc-dc converter |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103326622A (en) * | 2013-06-19 | 2013-09-25 | 国家电网公司 | Photovoltaic system suitable for high-voltage direct-current transmission |
| CN104269838A (en) * | 2013-09-24 | 2015-01-07 | 许继集团有限公司 | Valve level control method for flexible DC power transmission system |
| CN104218833A (en) * | 2014-05-26 | 2014-12-17 | 长沙理工大学 | Flexible voltage-sharing modulation method for capacitors of slave modules of modular multilevel converters |
| CN104135177A (en) * | 2014-07-24 | 2014-11-05 | 华北电力大学 | Voltage balancing control method applicable for sub-module capacitor voltage hierarchy of high-level MMC (Modular Multilevel Converter) |
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