CN103326607A - Single-inductance modular multi-level converter and control method thereof - Google Patents

Abstract

The invention provides a single-inductance modular multi-level converter and a control method of the single-inductance modular multi-level converter. Each phase of the single-inductance modular multi-level converter is composed of an upper bridge arm, an upper bridge arm inductor and a lower bridge arm, wherein the upper bridge arm, the upper bridge arm inductor and the lower bridge arm are connected in series, and each bridge arm is composed of a plurality of power sub-modules which are connected in series. Each SM is composed of a semi-bridge inversion unit and a direct-current energy-storing capacitor. Each semi-bridge inversion unit is formed by two full-control electronic power switching devices which are connected in series, wherein each full-control electronic power switch is provided with an anti-parallel diode. The direct-current energy-storing capacitor is connected with the two full-control electronic power switching devices in parallel. The control method of the single-inductance modular multi-level converter is capable of enabling the upper bridge arm and the lower bridge arm of the converter to symmetrically operate.

Description

Single many level current transformers of inductor moduleization and control method thereof

Technical field

The present invention relates to a kind of topological structure and control method thereof of multilevel power electronic inverter.

Background technology

Modular multi-level converter (Modular Multilevel Converter, MMC) is a kind of novel electric power electric current transformer that obtains recently extensive concern, is that A.Lesnicar and the R.Marquardt by Germany proposed about 2002 the earliest.Modular multi-level converter modularization and structures shape that can cascade its be pressed onto the application scenario of high-tension electricity electronics unsteady flow in being specially adapted to.About the control method of modular multi-level converter, correlative study mechanism has carried out more research both at home and abroad.

As shown in Figure 1, the Basic Topological of three-phase modular multilevel current transformer is to be made of six brachium pontis of three-phase.

Whenever, be followed in series to form by up and down two brachium pontis and AC reactor, each brachium pontis is made of several power submodules (SM) series connection.Each SM submodule is made of a semi-bridge inversion unit and a dc energy storage electric capacity, and each semi-bridge inversion unit is in series by two full control electronic power switch devices with anti-paralleled diode.By conducting and the shutoff of control electronic power switch device, each the exportable voltage 0 in SM submodule two ends or capacitance voltage when setting SM submodule output voltage 0, are assert this submodule conducting, when SM submodule output capacitance magnitude of voltage, assert that this submodule turn-offs.Can realize that with shutoff direct voltage is to the conversion of alternating voltage by the conducting of controlling each SM submodule so.

It is more that current transformer forms device, and cost is higher.In current transformer control Dead Time, the voltage that is added on the reactor is very high, even near DC bus-bar voltage, and rated operational voltage and the insulation level of reactor all proposed higher requirement, and the brachium pontis AC reactor that therefore forms current transformer is very expensive.

Summary of the invention

The objective of the invention is to overcome the existing high shortcoming of three-phase modular multilevel current transformer cost, propose the many level current transformers of a kind of single inductor moduleization.

The many level current transformers of the single inductor moduleization of the present invention are made of six brachium pontis of three-phase, and every have up and down two brachium pontis mutually.Every brachium pontis of going up is mutually formed by a brachium pontis inductance submodule cascade identical with several structures, and every brachium pontis that descends is mutually only formed by the identical submodule cascade of several structures.Each submodule is made of a semi-bridge inversion unit and a dc energy storage Capacitance parallel connection, described semi-bridge inversion unit is composed in series by two full control electronic power switch devices with anti-paralleled diode, and dc energy storage electric capacity is in parallel with two that connect full control electronic power switch devices.

The present invention is directed to the unsymmetric structure that brachium pontis is only formed by the identical submodule cascade of several structures under the many level current transformers of single inductor moduleization, proposed a kind of control method, control method of the present invention can be so that the upper and lower brachium pontis symmetrical operation of the current transformer of this unsymmetric structure.Control method of the present invention may further comprise the steps:

(1) with every brachium pontis and the lower brachium pontis electric current gone up mutually of current sensor measurement, calculates each phase current i _Out:

_iout＝i _up-i _down

I wherein _UpBrachium pontis electric current in the expression, i _DownThe lower brachium pontis electric current of expression;

(2) according to conservation of energy condition, calculate the set-point i of DC side input current transformer electric current _In ^*, the set-point i of DC side input current transformer electric current _In ^*Expression formula be:

i _in ^*＝P/U _dc

U wherein _DcExpression DC side busbar voltage records with voltage sensor, and P represents the single-phase average power of AC output;

(3) calculate the mean value of each direct current submodule voltage sum of upper and lower brachium pontis, mean value and the DC side bus voltage value of each direct current submodule voltage sum of upper and lower brachium pontis are subtracted each other, the difference of gained is sent in the pi regulator, the result who obtains joins in the set-point of DC side input current transformer electric current as the correction of output current of converter;

(4) according to upper brachium pontis current i _UpWith AC output current i _Out, calculate the actual value i that DC side is inputted the current transformer electric current _In, its expression formula is:

i _in＝i _up-0.5i _out；

(5) DC side is inputted the set-point i of current transformer electric current _In ^*With actual value i _InDifference send in the pi regulator, the result who obtains is the correction value Δ (u of bridge arm voltage _Up+ u _Down), u _UpWith u _DownRepresent respectively upper bridge arm voltage and lower bridge arm voltage;

(6) measure upper bridge arm voltage u with voltage sensor _L, send into band pass filter (Band Pass) extraction fundametal compoment u wherein _L0, and calculate the compensate component u' of lower bridge arm voltage _L, its expression formula is:

u' _L＝u _L-2u _L0；

(7) according to the given magnitude of voltage of AC

DC side busbar voltage U _Dc, bridge arm voltage correction value Δ (u _Up+ u _Down) and lower bridge arm voltage compensate component u' _LCalculate the given voltage of brachium pontis Given voltage with lower brachium pontis

Its expression formula is:

$u_{\mathrm{up}}^{*}=\frac{U_{\mathrm{dc}}}{2}-u_{\mathrm{out}}^{*}+0.5\×\mathrm{\Δ}(u_{\mathrm{up}}+u_{\mathrm{down}})$

$u_{\mathrm{down}}^{*}=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; dc"\; filenames="HDA00003294835600011.png,HDA00003294835600012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{\mathrm{dc}}}{2}+u_{\mathrm{out}}^{*}+0.5\&times;\mathrm{\&Delta;}(u_{\mathrm{up}}+u_{\mathrm{down}})+u_L^{\&prime;};$

(8) according to the given voltage of the upper brachium pontis that obtains in the step (7)

Given voltage with lower brachium pontis

Brachium pontis is opened number of modules n in the calculating _UpOpen number of modules n with lower brachium pontis _Down:

$n_{\mathrm{up}}=u_{\mathrm{up}}^{*}/U_c^{*}$

$n_{\mathrm{down}}=u_{\mathrm{down}}^{*}/U_c^{*}$

Wherein

Representation module capacitance voltage set-point;

(9) size of measurement described modular multi-level converter each submodule of each brachium pontis (SM) dc capacitor voltage is arranged sequentially with the capacitance voltage of measuring; Upper bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Up_1}, p _{Up_2}..., p _{Up_N}Upper bridge arm module voltage is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Up_1}, q _{Up_2}..., q _{Up_N}Lower bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Down_1}, p _{Down_2}, p _{Down_N}Lower bridge arm module is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Down_1}, q _{Down_2}, q _{Down_N}, wherein N represents each bridge arm module number;

(10) select the upper required module of opening of brachium pontis according to upper brachium pontis electric current: if upper brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Up_1}, p _{Up_2}..., Module; If upper brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Up_1}, q _{Up_2}..., q

Module;

(11) select the lower required module of opening of brachium pontis according to lower brachium pontis electric current: if lower brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Down_1}, p _{Down_2}, Module; If lower brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Down_1}, q _{Down_2}, q _{Down_down}Module.

The invention has the advantages that:

(1) the many level current transformers of the single inductor moduleization of the present invention have saved three brachium pontis inductance than original current transformer, simplify the structure, and have saved expense, have reduced cost;

(2) the single many level current transformers of inductor moduleization of the present invention control method can be so that the upper and lower brachium pontis symmetrical operation of current transformer.

Description of drawings

Fig. 1 is existing three-phase modular multilevel current transformer Basic Topological schematic diagram;

Fig. 2 is the single many level current transformers of inductor moduleization of the present invention Basic Topological schematic diagram;

Fig. 3 is the control method schematic diagram of the many level current transformers of the single inductor moduleization of the present invention;

Fig. 4 is the experimental waveform figure of the many level current transformers of the single inductor moduleization of the present invention.

Embodiment

The invention will be further described below in conjunction with the drawings and specific embodiments.

Fig. 2 is single many level current transformers of inductor moduleization Basic Topological schematic diagram of the present invention.As shown in Figure 2, current transformer is every to be made of upper brachium pontis, upper brachium pontis inductor and the series connection of lower brachium pontis, and upper brachium pontis and the series connection of upper brachium pontis inductor are again with lower brachium pontis series connection.Compare with traditional modular multi-level converter, lower brachium pontis is not established reactor, thereby has saved three reactors, has simplified the structure of time brachium pontis.Each brachium pontis is made of several power submodules SM series connection.Each submodule SM is made of a semi-bridge inversion unit and a dc energy storage electric capacity, each semi-bridge inversion unit is composed in series by two full control electronic power switch devices with anti-paralleled diode, and dc energy storage electric capacity is in parallel with two that connect full control electronic power switch devices.By conducting and the shutoff of controlling described electronic power switch device, each exportable magnitude of voltage in submodule SM two ends is 0 or the capacitance voltage value, and setting submodule SM output voltage values is 0 o'clock, assert this submodule conducting, when submodule SM output capacitance magnitude of voltage, assert that this submodule turn-offs.Can realize that with shutoff direct voltage is to the conversion of alternating voltage by the conducting of controlling each submodule SM.

Fig. 3 is the control method schematic diagram of the many level current transformers of novel single inductor moduleization of the present invention, and concrete steps are as follows:

(1) utilizes the every electric current of going up mutually brachium pontis and lower brachium pontis of current sensor measurement, calculate each phase current i _Out:

i _out＝i _up-i _down

I wherein _UpBrachium pontis electric current in the expression, i _DownThe lower brachium pontis electric current of expression;

(2) according to conservation of energy condition, calculate the set-point i of DC side input current transformer electric current _In ^*, the set-point i of DC side input current transformer electric current _In ^*Expression formula be:

i _in ^*＝P/U _dc

U wherein _DcExpression DC side busbar voltage, P represents the average power of the single-phase output of AC;

(3) calculate the mean value of each direct current submodule voltage sum of upper and lower brachium pontis: mean value and the DC side bus voltage value of each direct current submodule voltage sum of upper and lower brachium pontis are subtracted each other, the value of gained is sent in the pi regulator, the result who obtains joins the set-point i of DC side input current transformer electric current as the correction of output current of converter _In ^*In;

(4) according to upper brachium pontis current i _UpWith AC output current i _Out, calculate the actual value i that DC side is inputted the current transformer electric current _In, the actual value i of DC side input current transformer electric current _InExpression formula be:

i _in＝i _up-0.5i _out；

(5) DC side is inputted the set-point i of current transformer electric current _In ^*With actual value i _InDifference send in the pi regulator, the result who obtains is the correction value Δ (u of bridge arm voltage _Up+ u _Down), u _UpWith u _DownRepresent respectively upper bridge arm voltage and lower bridge arm voltage;

(6) measure upper bridge arm voltage u with voltage sensor _L, send into band pass filter (Band Pass) extraction fundametal compoment u wherein _L0, and calculate the compensate component u' of lower bridge arm voltage _L, its expression formula is:

u′ _L＝u _L-2u _L0；

(7) according to the given magnitude of voltage of AC

DC bus-bar voltage U _Dc, bridge arm voltage correction value Δ (u _Up+ u _Down) and lower bridge arm voltage compensate component u' _LCalculate the given voltage of brachium pontis Given voltage with lower brachium pontis

The given voltage of upper brachium pontis

Given voltage with lower brachium pontis Expression formula be:

$u_{\mathrm{up}}^{*}=\frac{U_{\mathrm{dc}}}{2}-u_{\mathrm{out}}^{*}+0.5\&times;\mathrm{\&Delta;}(u_{\mathrm{up}}+u_{\mathrm{down}})$

$u_{\mathrm{down}}^{*}=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; dc"\; filenames="HDA00003294835600011.png,HDA00003294835600012.png"\; state="\{\{state\}\}">U</figure-callout>}}_{\mathrm{dc}}}{2}+u_L^{\&prime;}+0.5\&times;\mathrm{\&Delta;}(u_{\mathrm{up}}+u_{\mathrm{down}})+u_L^{\&prime;};$

The given voltage of the upper brachium pontis that (8) obtains according to step (7)

Given voltage with lower brachium pontis

Brachium pontis is opened number of modules n in the calculating _UpOpen number of modules n with lower brachium pontis _Down:

$n_{\mathrm{up}}=u_{\mathrm{up}}^{*}/U_c^{*}$

$n_{\mathrm{down}}=u_{\mathrm{down}}^{*}/U_c^{*};$

(9) size of measurement described modular multi-level converter each submodule of each brachium pontis (SM) dc capacitor voltage, the capacitance voltage of measuring is arranged in order: upper bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Up_1}, p _{Up_2}..., p _{Up_N}Upper bridge arm module voltage is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Up_1}, q _{Up_2}..., q _{Up_N}Lower bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Down_1}, p _{Down_2}, p _{Down_N}Lower bridge arm module is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Down_1}, q _{Down_2}, q _{Down_N}, wherein N represents each bridge arm module number;

(10) according to upper brachium pontis electric current, the required module of opening of brachium pontis in the selection: if upper brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Up_1}, p _{Up_2}...,

Module; If upper brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Up_1}, q _{Up_2}...,

Module;

(11) according to lower brachium pontis electric current, select the lower required module of opening of brachium pontis: if lower brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Down_1}, p _{Down_2},

Module; If lower brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Down_1}, q _{Down_2}, q _{Down_down}Module.

Embodiment:

Below in conjunction with embodiment implementation result of the present invention is described.

Current transformer is operated in 50Hz in the present embodiment.

Fig. 4 is the experimental waveform figure of the many level current transformers of the single inductor moduleization of the present invention.Be followed successively by from top to bottom the electric current that three-phase current, the mutually upper and lower brachium pontis electric current of A, A phase DC side are input to current transformer among the figure, and the waveform of upper and lower bridge arm module average voltage.The as can be seen from the figure upper and lower brachium pontis electric current of current transformer full symmetric, upper and lower bridge arm module capacitance voltage almost symmetry.

As shown in Figure 4, adopt control method proposed by the invention, can make the upper and lower brachium pontis symmetrical operation of the single many level current transformers of inductor moduleization of the present invention.

Claims (2)

1. the many level current transformers of single inductor moduleization is characterized in that every the series connection by upper brachium pontis, upper brachium pontis inductor and lower brachium pontis of described current transformer consists of, and described upper brachium pontis and the series connection of upper brachium pontis inductance are again with lower brachium pontis series connection; Each brachium pontis is made of several power submodule (SM) series connection; Each submodule (SM) is made of a semi-bridge inversion unit and a dc energy storage electric capacity, each semi-bridge inversion unit is composed in series by two full control electronic power switch devices with anti-paralleled diode, and dc energy storage electric capacity is in parallel with two that connect full control electronic power switch devices.

2. the control method of the many level current transformers of single inductor moduleization claimed in claim 1 is characterized in that described control method comprises the steps:

(1) measures every phase upper and lower bridge arm electric current, calculate each phase current i _Out:

i _out＝i _up-i _down

I wherein _UpBrachium pontis electric current in the expression, i _DownThe lower brachium pontis electric current of expression;

(2) according to conservation of energy condition, calculate the set-point i of DC side input current transformer electric current _In ^*, the set-point i of DC side input current transformer electric current _In ^*Expression formula is:

i _in ^*＝P/U _dc

U wherein _DcExpression DC side busbar voltage, P represents the average power of the single-phase output of AC;

(3) calculate the mean value of each direct current submodule voltage sum of upper and lower brachium pontis, mean value and the DC side bus voltage value of each direct current submodule voltage sum of upper and lower brachium pontis are subtracted each other, the value of gained is sent in the pi regulator, the result who obtains joins the set-point i of DC side input current transformer electric current as the correction of output current of converter _In ^*In;

(4) according to upper brachium pontis current i _UpWith AC output current i _Out, calculate the actual value i that DC side is inputted the current transformer electric current _In, the actual value i of DC side input current transformer electric current _InExpression formula be:

i _in＝i _up-0.5i _out

(5) DC side is inputted the set-point i of current transformer electric current _In ^*With actual value i _InDifference send in the pi regulator, the result who obtains is the correction value Δ (u of bridge arm voltage _Up+ u _Down), u _UpWith u _DownRepresent respectively upper bridge arm voltage and lower bridge arm voltage;

(6) bridge arm voltage u in the measurement _L, send into band pass filter extraction fundametal compoment u wherein _L0, and calculate the compensate component u' of lower bridge arm voltage _L, the compensate component u' of lower bridge arm voltage _LExpression formula be:

u′ _L＝u _L-2u _L0；

(7) according to the given magnitude of voltage of AC

DC side busbar voltage U _Dc, bridge arm voltage correction value Δ (u _Up+ u _Down) and lower bridge arm voltage compensate component u' _L, calculate given voltage

With the given voltage of lower brachium pontis

Its expression formula is:

$u_{\mathrm{up}}^{*}=\frac{U_{\mathrm{dc}}}{2}-u_{\mathrm{out}}^{*}+0.5\&times;\mathrm{\&Delta;}(u_{\mathrm{up}}+u_{d\mathrm{own}})$

$u_{\mathrm{down}}^{*}=\frac{U_{\mathrm{dc}}}{2}+u_{\mathrm{out}}^{*}+0.5\&times;\mathrm{\&Delta;}(u_{\mathrm{up}}+u_{\mathrm{down}})+u_L^{\&prime;};$

The given voltage of the upper brachium pontis that (8) obtains according to step (7)

Given voltage with lower brachium pontis

Brachium pontis is opened number of modules n in the calculating _UpOpen number of modules n with lower brachium pontis _Down:

$n_{\mathrm{up}}=u_{\mathrm{up}}^{*}/U_c^{*}$

$n_{\mathrm{down}}=u_{\mathrm{down}}^{*}/U_c^{*}$

Wherein Representation module capacitance voltage set-point;

(9) measure the size of described modular multi-level converter each submodule of each brachium pontis (SM) dc capacitor voltage, the capacitance voltage of measuring is arranged sequentially: upper bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Up_1}, p _{Up_2}..., p _{Up_N}Upper bridge arm module voltage is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Up_1}, q _{Up_2}..., q _{Up_N}Lower bridge arm module is according to ascending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by p _{Down_1}, p _{Down_2}, p _{Down_N}Lower bridge arm module is according to descending arranged sequentially of capacitance voltage, and the module sequence number is followed successively by q _{Down_1}, q _{Down_2}, q _{Down_N}, wherein N represents each bridge arm module number;

(10) select the upper required module of opening of brachium pontis according to upper brachium pontis electric current: if upper brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Up_1}, p _{Up_2}...,

Module; If upper brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Up_1}, q _{Up_2}...,

Module;

(11) select the lower required module of opening of brachium pontis according to lower brachium pontis electric current: if lower brachium pontis electric current is then opened sequence number and is respectively p greater than 0 _{Down_1}, p _{Down_2}, Module; If lower brachium pontis electric current less than 0, is then opened sequence number and is respectively q _{Down_1}, q _{Down_2}, q _{Down_down}Module.

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