CN103326607B - Single inductor module Multilevel Inverters and control method thereof - Google Patents

Abstract

The present invention proposes a kind of single inductor module Multilevel Inverters and control method thereof, described current transformer every in series by upper brachium pontis, upper brachium pontis inductor and lower brachium pontis.Each brachium pontis is in series by several power modules (SM).Each submodule (SM) is made up of a semi-bridge inversion unit and a DC energy storage electric capacity, each semi-bridge inversion unit is formed by the full control electronic power switch devices in series of two band anti-paralleled diodes, and DC energy storage electric capacity controls the parallel connection of electronic power switch device entirely with two that connect.Control method of the present invention can make the upper and lower brachium pontis symmetrical operation of current transformer.

Description

Single inductor module Multilevel Inverters 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 (ModularMultilevelConverter, MMC) is a kind of novel electric power electric current transformer obtaining extensive concern recently, is the earliest to be proposed at about 2002 years by A.Lesnicar and R.Marquardt of Germany.Modular multi-level converter modularization and can cascade structures shape its be specially adapted in be pressed onto the application scenario of high-tension electricity electronics unsteady flow.About the control method of modular multi-level converter, domestic and international related research institutes has carried out more research.

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

Often be followed in series to form by upper and lower two brachium pontis and AC reactor, each brachium pontis is in series by several power modules (SM).Each SM submodule is made up of a semi-bridge inversion unit and a DC energy storage electric capacity, and each semi-bridge inversion unit is formed by the full control electronic power switch devices in series of two band anti-paralleled diodes.By controlling conducting and the shutoff of electronic power switch device, the exportable voltage 0 in each SM submodule two ends or capacitance voltage, during setting SM submodule output voltage 0, assert this submodule conducting, when SM submodule output capacitance magnitude of voltage, assert that this submodule turns off.Conducting so by controlling each SM submodule can realize the conversion of direct voltage to alternating voltage with shutoff.

Current transformer composition device is more, and cost is higher.Within the current transformer controlling dead error time, the voltage be added on reactor is very high, and even close to DC bus-bar voltage, be proposed higher requirement to the rated operational voltage of reactor and insulation level, the brachium pontis AC reactor therefore forming current transformer is very expensive.

Summary of the invention

The object of the invention is to overcome the high shortcoming of existing three-phase modular multilevel current transformer cost, propose a kind of single inductor module Multilevel Inverters.

List inductor module Multilevel Inverters of the present invention is made up of three-phase six brachium pontis, often has upper and lower two brachium pontis mutually.Every brachium pontis of going up mutually is formed by the sub module cascade that brachium pontis inductance is identical with several structures, often descends brachium pontis only to be formed by the sub module cascade that several structures are identical mutually.Each submodule is made up of a semi-bridge inversion unit and a DC energy storage Capacitance parallel connection, described semi-bridge inversion unit is made up of the full control electronic power switch devices in series of two band anti-paralleled diodes, and DC energy storage electric capacity controls the parallel connection of electronic power switch device entirely with two that connect.

The present invention is directed to brachium pontis under single inductor module Multilevel Inverters only by the unsymmetric structure of the identical sub module cascade of several structures, propose a kind of control method, control method of the present invention can make the upper and lower brachium pontis symmetrical operation of the current transformer of this unsymmetric structure.Control method of the present invention comprises the following steps:

(1) often go up brachium pontis and lower bridge arm current mutually with current sensor measurement, calculate each phase current i _out:

i _out＝i _up-i _down

Wherein i _upbridge arm current in expression, i _downrepresent lower bridge arm current;

(2) according to conservation of energy condition, the set-point i of DC side input current transformer electric current is calculated _in ^*, the set-point i of DC side input current transformer electric current _in ^*expression formula be:

i _in ^*＝P/U _dc

Wherein U _dcrepresent DC side busbar voltage, record with voltage sensor, P represents the single-phase average power that AC exports;

(3) mean value of brachium pontis each direct current submodule voltage is calculated respectively with the mean value of lower brachium pontis each direct current submodule voltage both are added the mean value obtaining this phase bridge arm module voltage divided by 2, by itself and module capacitance voltage given value subtract each other, the value of gained sent in pi regulator, the result obtained, as the correction of output current of converter, joins the set-point i of DC side input current transformer electric current _in ^*in;

(4) according to upper bridge arm current i _upwith AC output current i _out, calculate the actual value i of DC side input 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 pi regulator, the result obtained is the correction value △ (u of bridge arm voltage _up+ u _down), u _upwith u _downrepresent upper bridge arm voltage and lower bridge arm voltage respectively;

(6) upper brachium pontis inductive drop u is measured with voltage sensor _l, send into band pass filter (BandPass) 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 △ (u _up+ u _down) and lower bridge arm voltage compensate component u' _lcalculate the given voltage of brachium pontis with the given voltage of lower brachium pontis its expression formula is:

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

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

(8) according to the given voltage of the upper brachium pontis obtained in step (7) with the given voltage of lower brachium pontis in calculating, brachium pontis opens number of modules n _upnumber of modules n is opened with lower brachium pontis _down:

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

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

Wherein representation module capacitance voltage set-point;

(9) size of each brachium pontis of modular multi-level converter each submodule (SM) DC capacitor voltage described in measurement, by the capacitance voltage order arrangement of measuring; Upper bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{up_1}, p _{up_2}..., p _{up_N}; Upper bridge arm module voltage arranges according to the order that capacitance voltage is descending, and module sequence number is followed successively by q _{up_1}, q _{up_2}..., q _{up_N}; Lower bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{down_1}, p _{down_2}, p _{down_N}; Lower bridge arm module arranges according to the order that capacitance voltage is descending, and 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 to open module needed for upper brachium pontis according to upper bridge arm current: if upper bridge arm current is greater than 0, then opens sequence number and be respectively module; If upper bridge arm current is less than 0, then opens sequence number and be respectively module;

(11) select to open module needed for lower brachium pontis according to lower bridge arm current: if lower bridge arm current is greater than 0, then opens sequence number and be respectively module; If lower bridge arm current is less than 0, then opens sequence number and be respectively module.

The invention has the advantages that:

(1) list inductor module Multilevel Inverters of the present invention eliminates three brachium pontis inductance than original current transformer, simplifies the structure, saves expense, reduce cost;

(2) list inductor module Multilevel Inverters control method of the present invention can make the upper and lower brachium pontis symmetrical operation of current transformer.

Accompanying drawing explanation

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

Fig. 2 is list inductor module Multilevel Inverters Basic Topological schematic diagram of the present invention;

Fig. 3 is the control method schematic diagram of list inductor module Multilevel Inverters of the present invention;

Fig. 4 is the experimental waveform figure of list inductor module Multilevel Inverters of the present invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described.

Fig. 2 is single inductor module Multilevel Inverters Basic Topological schematic diagram of the present invention.As shown in Figure 2, current transformer is every in series by upper brachium pontis, upper brachium pontis inductor and lower brachium pontis, upper brachium pontis and the series connection of upper brachium pontis inductor, then connects with lower brachium pontis.Compared with traditional modular multi-level converter, lower brachium pontis does not establish reactor, thus saves three reactors, simplifies the structure of lower brachium pontis.Each brachium pontis is in series by several power modules SM.Each submodule SM is made up of a semi-bridge inversion unit and a DC energy storage electric capacity, each semi-bridge inversion unit is made up of the full control electronic power switch devices in series of two band anti-paralleled diodes, and DC energy storage electric capacity controls the parallel connection of electronic power switch device entirely with two that connect.By controlling conducting and the shutoff of described electronic power switch device, the exportable magnitude of voltage in each submodule SM two ends is 0 or capacitance voltage value, when setting submodule SM output voltage values is 0, assert this submodule conducting, when submodule SM output capacitance magnitude of voltage, assert that this submodule turns off.The conversion of direct voltage to alternating voltage can be realized with shutoff by the conducting controlling each submodule SM.

Fig. 3 is the control method schematic diagram of novel single inductor module Multilevel Inverters of the present invention, and concrete steps are as follows:

(1) utilize current sensor measurement often to go up the electric current of brachium pontis and lower brachium pontis mutually, calculate each phase current i _out:

i _out＝i _up-i _down

Wherein i _upbridge arm current in expression, i _downrepresent lower bridge arm current;

(2) according to conservation of energy condition, the set-point i of DC side input current transformer electric current is calculated _in ^*, the set-point i of DC side input current transformer electric current _in ^*expression formula be:

i _in ^*＝P/U _dc

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

(3) mean value of brachium pontis each direct current submodule voltage is calculated respectively with the mean value of lower brachium pontis each direct current submodule voltage both are added the mean value obtaining this phase bridge arm module voltage divided by 2, by itself and module capacitance voltage given value subtract each other, the value of gained sent in pi regulator, the result obtained, as the correction of output current of converter, joins the set-point i of DC side input current transformer electric current _in ^*in; (4) according to upper bridge arm current i _upwith AC output current i _out, calculate the actual value i of DC side input 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 pi regulator, the result obtained is the correction value △ (u of bridge arm voltage _up+ u _down), u _upwith u _downrepresent upper bridge arm voltage and lower bridge arm voltage respectively;

(6) upper brachium pontis inductive drop u is measured with voltage sensor _l, send into band pass filter (BandPass) 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 △ (u _up+ u _down) and lower bridge arm voltage compensate component u' _lcalculate the given voltage of brachium pontis with the given voltage of lower brachium pontis the given voltage of upper brachium pontis with the given voltage of lower brachium pontis expression formula be:

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

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

(8) the given voltage of the upper brachium pontis obtained according to step (7) with the given voltage of lower brachium pontis in calculating, brachium pontis opens number of modules n _upnumber of modules n is opened with lower brachium pontis _down:

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

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

(9) size of each brachium pontis of modular multi-level converter each submodule (SM) DC capacitor voltage described in measurement, the capacitance voltage of measurement is arranged in order: upper bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{up_1}, p _{up_2}..., p _{up_N}; Upper bridge arm module voltage arranges according to the order that capacitance voltage is descending, and module sequence number is followed successively by q _{up_1}, q _{up_2}..., q _{up_N}; Lower bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{down_1}, p _{down_2}, p _{down_N}; Lower bridge arm module arranges according to the order that capacitance voltage is descending, and 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 bridge arm current, selection opens module needed for brachium pontis: if upper bridge arm current is greater than 0, then opens sequence number and be respectively module; If upper bridge arm current is less than 0, then opens sequence number and be respectively module;

(11) according to lower bridge arm current, select to open module needed for lower brachium pontis: if lower bridge arm current is greater than 0, then opens sequence number and be respectively module; If lower bridge arm current is less than 0, then opens sequence number and be respectively 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 list inductor module Multilevel Inverters of the present invention.Be followed successively by three-phase current in figure from top to bottom, electric current that the upper and lower bridge arm current of A phase, A phase DC side are input to current transformer, and the waveform of upper and lower bridge arm module average voltage.As can be seen from the figure the upper and lower bridge arm current full symmetric of current transformer, upper and lower bridge arm module capacitance voltage almost symmetry.

As shown in Figure 4, adopt control method proposed by the invention, the upper and lower brachium pontis symmetrical operation of list inductor module Multilevel Inverters of the present invention can be made.

Claims (2)

1. a single inductor module Multilevel Inverters, is characterized in that described current transformer is every in series by upper brachium pontis, upper brachium pontis inductor and lower brachium pontis, described upper brachium pontis and the series connection of upper brachium pontis inductance, then connects with lower brachium pontis; Each brachium pontis is in series by several power modules (SM); Each submodule (SM) is made up of a semi-bridge inversion unit and a DC energy storage electric capacity, each semi-bridge inversion unit is made up of the full control electronic power switch devices in series of two band anti-paralleled diodes, and DC energy storage electric capacity controls the parallel connection of electronic power switch device entirely with two that connect.

2. the control method of single inductor module Multilevel Inverters according to claim 1, is characterized in that described control method comprises the steps:

(1) measure every phase upper and lower bridge arm electric current, calculate each cross streams side output current i _out:

i _out＝i _up-i _down

Wherein i _upbridge arm current in expression, i _downrepresent lower bridge arm current;

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

i _in ^*＝P/U _dc

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

(3) mean value of brachium pontis each direct current submodule voltage is calculated respectively with the mean value of lower brachium pontis each direct current submodule voltage both are added the mean value obtaining this phase bridge arm module voltage divided by 2, by itself and module capacitance voltage given value subtract each other, the value of gained sent in pi regulator, the result obtained, as the correction of output current of converter, joins the set-point i of DC side input current transformer electric current _in ^*in;

(4) according to upper bridge arm current i _upwith AC output current i _out, calculate the actual value i of DC side input 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 pi regulator, the result obtained is the correction value △ (u of bridge arm voltage _up+ u _down), u _upwith u _downrepresent upper bridge arm voltage and lower bridge arm voltage respectively;

(6) brachium pontis inductive drop u in 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 △ (u _up+ u _down) and lower bridge arm voltage compensate component u' _l, calculate the given voltage of brachium pontis with the given voltage of lower brachium pontis its expression formula is:

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

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

(8) the given voltage of the upper brachium pontis obtained according to step (7) with the given voltage of lower brachium pontis in calculating, brachium pontis opens number of modules n _upnumber of modules n is opened with lower brachium pontis _down:

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

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

Wherein representation module capacitance voltage set-point;

(9) size of each brachium pontis of modular multi-level converter each submodule (SM) the DC energy storage capacitance voltage described in measurement, capacitance voltage order arrangement by measuring: upper bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{up_1}, p _{up_2}..., p _{up_N}; Upper bridge arm module voltage arranges according to the order that capacitance voltage is descending, and module sequence number is followed successively by q _{up_1}, q _{up_2}..., q _{up_N}; Lower bridge arm module arranges according to the order that capacitance voltage is ascending, and module sequence number is followed successively by p _{down_1}, p _{down_2}, p _{down_N}; Lower bridge arm module arranges according to the order that capacitance voltage is descending, and 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 to open module needed for upper brachium pontis according to upper bridge arm current: if upper bridge arm current is greater than 0, then opens sequence number and be respectively module; If upper bridge arm current is less than 0, then opens sequence number and be respectively module;

(11) select to open module needed for lower brachium pontis according to lower bridge arm current: if lower bridge arm current is greater than 0, then opens sequence number and be respectively module; If lower bridge arm current is less than 0, then opens sequence number and be respectively module.