CN203590069U - Mixed type multi-level converter based on full-bridge module and half-bridge module - Google Patents

Abstract

The utility model discloses a mixed type multi-level converter based on a full-bridge module and a half-bridge module. The mixed type multi-level converter comprises three phase units connected between a positive electrode DC bus and a negative electrode DC bus, wherein each of the phase units is composed of an upper bridge arm and a lower bridge arm, each bridge arm comprises N half-bridge modules and a full-bridge module with a DC power supply, the N half-bridge modules and the full-bridge module with the DC power supply are connected in series, and the N is an integer. The mixed type multi-level converter realizes a high number of output levels by using as few as the half-bridge modules, the consumed calculation time is less and the efficiency is higher when a sorting algorithm is carried out on voltage of the half-bridge modules, the input speed of the modules is accelerated, and voltage fluctuation of a capacitor can be reduced.

Description

Mixed type multilevel converter based on full-bridge and half-bridge module

Technical field

The utility model relates to modularization multi-level converter field, particularly a kind of mixed type multilevel converter based on full-bridge and half-bridge module.

Background technology

In the direct current transportation field based on voltage source converter, what use the earliest is two level topological structures, and its switching device is withstand voltage to be all restricted with through-put power, and need to add output filtering device.For addressing these problems, voltage with multiple levels source converter starts to occur and be subject to increasing concern.These multilevel converters can be divided into three major types principle: the first kind is clamped multi-level structure; Equations of The Second Kind is to utilize the directly tandem type version of overlapped in series of single-phase full bridge converter (being H bridge); The 3rd class forms submodule unit by electric capacity and half-bridge switch device, consists of the version of many level outputs sub-series modular unit between the positive and negative DC bus of converter.Wherein first kind topological structure is along with the increasing of output level number, and required clamping diode or flying capacitor will sharply increase, and to system control and production, assembling, brings great difficulty.Although Equations of The Second Kind topological structure has been realized modularization, be easy to expand, the number of the independent DC power supply needing is more.The 3rd class topological structure is that MMC has plurality of advantages: manufacture difficulty reduces, loss declines at double, step voltage reduces, waveform quality is high, troubleshooting capability is strong etc., is therefore also applied widely.What the U.S. " the Trans Bay Cable Project " converter putting into operation in 2010 adopted is exactly this MMC structure.The domestic Shanghai Nanhui flexible DC power transmission engineering of having built up, and be about to start this MMC topological structure being formed by half-bridge submodule that all adopts of Zhoushan Of Zhejiang Province multiterminal flexible direct current engineering, Dalian flexible direct current engineering, Generated By Nanao Wind Power Plants flexible DC power transmission engineering of building.

In order further to improve performance, some scholars, by proposing the mixed type multilevel converter topological structure based on full-bridge and half-bridge module, can make the performance of converter more perfect under the prerequisite of advantage that keeps MMC.As passed through to introduce two three brachium pontis power cells in paper " a kind of novel four-quadrant mixed type module combination multi-level converter ", make, under identical output and input level condition, to have reduced direct current capacitor quantity and the capacitance of power cell.The mixed type multilevel converter of paper " the flexible DC power transmission system based on mixed type multilevel converter " research, except having the basic characteristics of multilevel converter, also has higher direct voltage utilance, stronger DC Line Fault tolerance.But the number of modules needing and the number of switching device are still a lot, aspect raising output level number, rarely having progress.

Utility model content

In order to overcome the above-mentioned shortcoming and deficiency of prior art, the purpose of this utility model is to provide a kind of mixed type multilevel converter based on full-bridge and half-bridge module, utilizes the least possible half-bridge module number to realize the output level number that converter is higher.

The purpose of this utility model is achieved through the following technical solutions:

Mixed type multilevel converter based on full-bridge and half-bridge module, comprise the three phase units being connected between both positive and negative polarity DC bus, each facies unit is comprised of upper brachium pontis and lower brachium pontis, each brachium pontis comprises N half-bridge module and 1 full-bridge module with DC power supply, a described N half-bridge module and 1 full-bridge module with DC power supply are connected in series, and N is positive integer.

The described full-bridge module with DC power supply is comprised of four igbts with anti-paralleled diode and a DC power supply, the series connection of every two igbts order forms cascaded structure, and the two ends of each cascaded structure are connected with the two ends of DC power supply respectively; In each cascaded structure, the tie point of two igbts is one of them output of full-bridge module.

Described half-bridge module is comprised of two igbts with anti-paralleled diode and an electric capacity, described two igbts with anti-paralleled diode order is connected afterwards and Capacitance parallel connection, the output that described two series connection points with the igbt of anti-paralleled diode are described half-bridge module, another output that any one end of described electric capacity is described half-bridge module.

Compared with prior art, the utlity model has following advantage and beneficial effect:

Mixed type multilevel converter based on full-bridge and half-bridge module of the present utility model, by adding the full-bridge module with DC power supply on the MMC topological structure traditional, utilizes the least possible half-bridge module number to realize the output level number that converter is higher.Due to half-bridge module decreased number, when the capacitance voltage of half-bridge module is carried out to sort algorithm, calculate still less efficiency consuming time higher, module input speed is accelerated, and can reduce voltage fluctuation of capacitor.Adopt multilevel converter of the present utility model not only can save IGBT(igbt) number and electric capacity number, by increasing number of levels, improved the quality of power supply simultaneously, make the harmonic content of output variable less.

Accompanying drawing explanation

Fig. 1 is the topology diagram of the mixed type multilevel converter based on full-bridge and half-bridge module of embodiment of the present utility model.

Fig. 2 is the topology diagram of the half-bridge module of embodiment of the present utility model.

Fig. 3 is the topology diagram of the full-bridge module of embodiment of the present utility model.

Fig. 4 is the output phase voltage comparison diagram of the mixed type multilevel converter based on full-bridge and half-bridge module of traditional MMC and the present embodiment.

Embodiment

Below in conjunction with embodiment, the utility model is described in further detail, but execution mode of the present utility model is not limited to this.

Embodiment

As shown in Figure 1, the mixed type multilevel converter based on full-bridge and half-bridge module of the present embodiment comprises the three phase units being connected between both positive and negative polarity DC bus, and each facies unit is comprised of upper brachium pontis and lower brachium pontis, and each brachium pontis comprises N half-bridge module (SM ₁, SM ₂,, SM _n) and a full-bridge module HB with DC power supply, a described N half-bridge module and a full-bridge module with DC power supply are connected in series, and N is positive integer.In figure, A, B and C represent respectively converter AC three-phase; L ₀represent brachium pontis reactor; U _dcfor the voltage difference between both positive and negative polarity DC bus.

As shown in Figure 2, the half-bridge module of the present embodiment is by the igbt VT1 with anti-paralleled diode D1, form with igbt VT2 and a capacitor C of anti-paralleled diode D2, in parallel with capacitor C after igbt VT1 and VT2 series connection, the series connection point of igbt VT1 and VT2 is an output of half-bridge module, another output that any one end of capacitor C is half-bridge module, U _crepresent half-bridge module capacitance voltage; U _sMrepresent half-bridge module port output voltage.

As shown in Figure 3, the full-bridge module with DC power supply of the present embodiment is by the igbt VT3 with anti-paralleled diode D3, with the igbt VT4 of anti-paralleled diode D4, with the igbt VT5 of anti-paralleled diode D5, with igbt VT6 and a DC power supply composition of anti-paralleled diode D6, igbt VT3, the series connection of VT5 order forms cascaded structure, igbt VT4, the series connection of VT6 order forms cascaded structure, the two ends of each cascaded structure are connected with the two ends of DC power supply respectively, the series connection point of igbt VT3, VT5 is one of them output of full-bridge module, and the series connection point of VT4, VT6 is another output of full-bridge module, U in figure _sfor DC source voltage, U _hMrepresent the output voltage of full-bridge module.

The control method of the mixed type multilevel converter based on full-bridge and half-bridge module of the present embodiment is:

S1 drops into number by nearest level approach method control half-bridge module, according to calculating the half-bridge module number that needs input, then according to the capacitance voltage ranking results of each half-bridge module and the brachium pontis sense of current, determine which half-bridge module of conducting, make the capacitance voltage of all half-bridge modules maintain balance;

The computational methods that described half-bridge module drops into number are as follows:

In each moment, every real-time expression formula of descending mutually the half-bridge module number that brachium pontis need drop into is:

$n_{\mathrm{down}}=\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000418757180000031.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}+\mathrm{round}\left(\frac{u_i}{U_C}\right)$

In each moment, every real-time expression formula that goes up mutually the half-bridge module number that brachium pontis need drop into is:

$n_{\mathrm{up}}=\frac{N}{2}-n_{\mathrm{down}}=\frac{N}{2}-\mathrm{round}\left(\frac{u_i}{U_C}\right)$

Wherein, U _cthe capacitance voltage of each half-bridge module while maintaining equilibrium for the capacitance voltage of all half-bridge modules, U _c=U _dc/ N; U _ifor phase voltage modulating wave; Round () represents to get immediate integer, as round (x) represents to get the immediate integer with x;

S2 is because full-bridge module has three kinds of output states, and selecting DC source voltage is U _c/ 3, by controlling the switching of full-bridge module, can in original every two level, insert 2 level, make level number be increased to 3N+1 from N+1;

The input state of the full-bridge module of upper brachium pontis is:

$S_{\mathrm{HB}}=\mathrm{MOD}(\frac{3}{2}N+\mathrm{round}\left(\frac{{3U}_i}{2/N}\right),3)i=a,b,c$

Wherein, U _ifor phase voltage modulating wave, MOD () represents complementation, as MOD (x, y) represents integer x, is removed the remainder of gained by integer y;

The input state of the full-bridge module of lower brachium pontis is:

S′ _HB=MOD(3-S _HB,3)。

The on off state of full-bridge module and input voltage corresponding relation are as shown in table 1 below, U _hMrepresent the output voltage of full-bridge module.

Table 1 full-bridge module switch state and the corresponding table of input voltage

Can in upper brachium pontis, full-bridge module input voltage be Us, lower brachium pontis full-bridge module drops into correspond to-Us of voltage; In lower brachium pontis, full-bridge module input voltage is 0 o'clock, and it is also 0 that lower brachium pontis full-bridge module drops into voltage.Can realize accordingly whole bridge arm voltage sum and equal DC line voltage.

The output phase voltage of traditional MMC that each brachium pontis contains 4 half-bridge modules and the mixed type multilevel converter of the present embodiment (take N=5 as example) contrasts as shown in Figure 4, wherein, the corresponding traditional MMC of dotted line, the corresponding the present embodiment of solid line, known, with respect to traditional MMC, the level number of the mixed type multilevel converter of the present embodiment is increased to 13 from 5.When requiring output-voltage levels number to be 13, if adopt traditional MMC structure, each brachium pontis needs 12 half-bridge modules, and comparatively speaking, if adopt scheme of the present utility model, six brachium pontis save 6*7=42 half-bridge module altogether.

Above-described embodiment is preferably execution mode of the utility model; but execution mode of the present utility model is not limited by the examples; other any do not deviate from change, the modification done under Spirit Essence of the present utility model and principle, substitutes, combination, simplify; all should be equivalent substitute mode, within being included in protection range of the present utility model.

Claims (3)

1. the mixed type multilevel converter based on full-bridge and half-bridge module, it is characterized in that, comprise the three phase units being connected between both positive and negative polarity DC bus, each facies unit is comprised of upper brachium pontis and lower brachium pontis, each brachium pontis comprises N half-bridge module and 1 full-bridge module with DC power supply, a described N half-bridge module and 1 full-bridge module with DC power supply are connected in series, and N is positive integer.

2. the mixed type multilevel converter based on full-bridge and half-bridge module according to claim 1, it is characterized in that, the described full-bridge module with DC power supply is comprised of four igbts with anti-paralleled diode and a DC power supply, the series connection of every two igbts order forms cascaded structure, and the two ends of each cascaded structure are connected with the two ends of DC power supply respectively; In each cascaded structure, the tie point of two igbts is one of them output of full-bridge module.

3. the mixed type multilevel converter based on full-bridge and half-bridge module according to claim 1, it is characterized in that, described half-bridge module is comprised of two igbts with anti-paralleled diode and an electric capacity, described two igbts with anti-paralleled diode order is connected afterwards and Capacitance parallel connection, the output that described two series connection points with the igbt of anti-paralleled diode are described half-bridge module, another output that any one end of described electric capacity is described half-bridge module.

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