CN105391313A - Control method of modular multi-level current converter - Google Patents

Control method of modular multi-level current converter Download PDF

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Publication number
CN105391313A
CN105391313A CN201511020648.6A CN201511020648A CN105391313A CN 105391313 A CN105391313 A CN 105391313A CN 201511020648 A CN201511020648 A CN 201511020648A CN 105391313 A CN105391313 A CN 105391313A
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module group
group
submodule
voltage
conducting
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CN105391313B (en
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黄守道
荣飞
陈盼庆
罗德荣
龚喜长
李旺
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Hunan University
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Hunan University
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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
    • 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
    • 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
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • 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
    • H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses a control method of a modular multi-level current converter. According to the control method, 2N sub modules of a bridge arm is divided into N+1 module groups according to 20, 21, 22, and so on, and 2N-1, and 1, and during work, intra-group sub modules in each group are kept the same in state, namely being simultaneously turned on or turned off. Each group is configured with a voltage sensor used for measuring the voltage value of the group. According to such a structure, a voltage stability control method, a voltage recording method, a modulation method and an even pressure control method are designed. Voltage stability control adopts a PI adjustor to stabilize the sum of capacitor voltage of all sub modules of all phases; the voltage recording method is used for saving voltage values of all the module groups; the modulation method is used for determining the on-off state of each module group; even pressure control is used for keeping the average value of the sub modules of a component to be balanced. According to the control method provided by the invention, a control way of grouping sub module groups is adopted, voltage transformers required in an MMC system are greatly reduced, and further, hardware complexity of the system is reduced and the cost of MMC is reduced.

Description

A kind of control method of modularization multi-level converter
Technical field
Patent of the present invention belongs to flexible direct-current transmission field, the method for particularly modularization multi-level converter control.
Background technology
Technology of HVDC based Voltage Source Converter is the effective way building flexible, strong, efficient electrical network and make full use of regenerative resource, represents the future thrust of direct current transportation, has become one of key technology of New Generation of Intelligent electrical network.The modularization multi-level converter of one of core devices in flexible transmission engineering, its stability, economy remains one of key point of restriction Technology of HVDC based Voltage Source Converter large-scale commercial applications operation.Patent of the present invention is set about from the economy improving modularization multi-level converter, under the prerequisite of the stability of the system of guarantee, reduces the quantity of submodule voltage sensor, and then reduces system cost.
The maximum advantage of Modularized multi-level converter sub-module cascade is, under the prerequisite of low voltage stress, is obtained the output voltage of voltage levels by submodule series connection.Therefore, in the engineering project of reality, every phase brachium pontis contains a large amount of submodules.One of Focal point and difficult point of modularization multi-level converter control strategy is that controlling each submodule capacitor voltage is stabilized in submodule reference voltage, and conventional control method has phase-shifting carrier wave and nearest level to approach.Two kinds of basic methods all need the voltage gathering storage capacitor in each submodule, and then determine conducting or the excision state of corresponding submodule by control algolithm.This pattern causes MMC system need configure a large amount of voltage sensors, and this adds the complexity of system undoubtedly and improves the cost of system.
The pattern that each submodule is equipped with a voltage sensor is not that converter normally runs essential condition, and the method being therefore much devoted to reduce voltage sensor occurs.The simplest method directly cancels voltage sensor, and the submodule setting every phase brachium pontis carries out conducting or shutoff according to certain control strategy, maintains submodule capacitor voltage stablize by presetting conducting with shutoff strategy.The reliability by greatly reducing system of this open loop control mode.Another kind of mode cut-offs status predication capacitance voltage by bridge arm current and DC bus-bar voltage zygote module.For improving the accuracy of prediction, some methods propose each brachium pontis and are equipped with a small amount of voltage sensor, and the submodule capacitor voltage of prediction resets by timing.These adopt the method for prediction capacitance voltage normally to run in system, and system is in of short duration uncontrollable state, and comparatively slow to the reaction of system abnormal condition, the reliability of system will be affected.
Summary of the invention
Technical problem solved by the invention is, for the deficiencies in the prior art, a kind of control method of modularization multi-level converter is provided, under the present invention can ensure the condition of output voltage waveforms engineering demands, significantly reduce the quantity of voltage sensor, and the quantity of the more minimizings of brachium pontis submodule quantity is more remarkable.
For achieving the above object, the technical solution used in the present invention is:
A control method for modularization multi-level converter, described modularization multi-level converter (MMC) adopts three-phase six bridge arm topological structure, and often comprise upper and lower two brachium pontis mutually, each brachium pontis is by 2 nindividual SM submodule and 1 inductance L are in series, and upper and lower brachium pontis tie point draws phase line; Article three, phase line access public electric wire net; N is integer, wherein, function is for rounding up; U dcfor the DC voltage by converter, U smfor SM submodule reference voltage;
Each SM submodule is a half-bridge current transformer, is made up of two IGBT pipe T1 and T2, two diode D1 and D2 and electric capacity C; Wherein, the emitter of IGBT pipe T1 is connected with the collector electrode of IGBT pipe T2 and forms the anode of SM, and the collector electrode of IGBT pipe T1 is connected with the positive pole of electric capacity C, and the emitter of IGBT pipe T2 is connected with the negative pole of electric capacity and forms the negative terminal of SM; D1 and T1 reverse parallel connection, D2 and T2 reverse parallel connection; The gate pole of IGBT pipe T1 and T2 all receives control wave;
Often go up 2 of brachium pontis mutually nindividual SM submodule and 1 inductance L are connected successively, and the anode namely going up brachium pontis first SM submodule is connected with DC side positive pole; The anode of i-th the SM submodule mediated is connected with the negative terminal of the i-th-1 SM submodule, and the negative terminal of i-th SM submodule is connected with the anode of the i-th+1 SM submodule, i=2, and 3 ..., 2 n-1; Upper brachium pontis the 2nd nthe negative terminal of individual SM submodule is connected with inductance L one end, and the inductance L other end draws phase line;
Every inductance L and 2 descending brachium pontis mutually nindividual SM submodule is connected successively, and namely phase line is drawn in inductance L one end, and the inductance L other end is connected with the anode of lower brachium pontis first SM submodule; The anode of i-th the SM submodule mediated is connected with the negative terminal of the i-th-1 SM submodule, i-th SM submodule negative terminal be connected with the anode of the i-th+1 SM submodule, i=2,3 ..., 2 n-1; Lower brachium pontis the 2nd nthe negative terminal of individual SM submodule is connected with DC side negative pole;
The neutral earthing of DC side power supply;
For the arbitrary phase in three-phase (A phase, B phase and C phase), described control method comprises the following steps:
Step 1, module are divided into groups;
Step 2, voltage stabilizing control, and adopt pi regulator to stablize the capacitance voltage sum of each mutually all submodules;
Step 3, modulation, be used for determining the on off operating mode of a module group;
The module grouping of described step 1, specifically comprises the following steps:
By 2 of each for converter brachium pontis nindividual SM submodule is divided into N+1 module group, and front N group respectively comprises 2 i-1individual SM submodule, i is the sequence number of module group, i=1,2 ..., (namely the 1st group comprises 2 to N 0individual SM submodule, the 2nd group comprises 2 1individual SM submodule, the 3rd group comprises 2 2individual SM submodule, the like, N group comprises 2 n-1individual SM submodule), N+1 group comprises 1 SM submodule; Each module group voltage sensor in parallel, for measuring the total voltage of SM submodule electric capacity in this module group; In work, often submodule state is consistent in group group, i.e. conducting simultaneously or shutoff;
The voltage stabilizing of described step 2 controls, and specifically comprises the following steps:
2.1) measure brachium pontis in this phase and, from first module group to the magnitude of voltage of N+1 module group, voltage measuring value is designated as U respectively aup1, U aup2...., U aupi...., U aup (N+1); Under measuring this phase, brachium pontis is from first module group to the magnitude of voltage of N+1 module group, and voltage measuring value is designated as U respectively abelow1, U abelow2..., U abelowi...., U abelow (N+1);
2.2) for N+1 module group of each brachium pontis, when certain module group is in conducting state, the voltage measuring value of this module group is preserved; To i-th the module group of brachium pontis in this phase, its voltage measuring value is saved as voltage record value U asupi; To i-th the module group of brachium pontis under this phase, its voltage measuring value is recorded as U asbelowi; Until upgrade this voltage record value after this module group conducting next time;
2.3) according to step 2.1) voltage measuring value that obtains calculates the voltage sum U of this mutually each module group afor:
U a = Σ i = 1 N + 1 U a u p i + Σ i = 1 N + 1 U a b e l o w i
2.4) the measurement moment is established to have the conducting of K module group, according to the output U that following formulae discovery voltage stabilizing controls aref1:
U aref1＝(U sm-U a/K)(K p+K i/s)
Wherein, K pfor proportionality coefficient, K ifor integral coefficient, 1/s is that (integrating factor is to (U to integrating factor sm-U a/ K) carry out integration, namely As time goes on, ceaselessly this error amount cumulative);
2.5) converter is set to need the voltage of output as U aref2, according to the modulation voltage U of following formulae discovery converter aref:
U aref＝U aref1+U aref2；
The modulation of described step 3, specifically comprises the following steps:
3.1) according to step 2.5) calculate modulation voltage U aref, calculate the conducting number N of brachium pontis and lower bridge arm module group in this phase respectively aupand N abelow:
N aup＝round((U dc/2-U aref)/U sm)
N abelow＝round((U dc/2+U aref)/U sm)
Wherein, round () is the function that rounds up;
3.2) by N aupbe converted into binary number, be designated as N naup; N naupeach from low level to a high position, respectively with upper brachium pontis the 1st to N number of module group one_to_one corresponding; According to N naupin each numerical value, following control is carried out to each module group:
3.2.1) work as N naupin when having at least 2 to equal 1, conducting N naupin equal the module group of the position correspondence of 1, turn off other module group and (comprise N naupin equal the module group of the position correspondence of 0 and N+1 module group);
3.2.2) work as N naupin everybody when being congruent to 0, all module groups of brachium pontis in shutoff;
3.2.3) work as N naupwhen only having 1 to equal 1, other everybody when all equaling 0, if the position equaling 1 is i-th, and set the measured value of bridge arm current in this phase as i aup;
If i aupdirection is SM charging direction, i.e. i aup>0, then adopt and carry out Pressure and Control as follows:
If (a) U asupi/ N aup>U smand i>1, then conducting the 1 to the i-th-1 module group and N+1 module group, turn off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup>U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup≤ U sm, then conducting i-th group of module group, and turn off other module group;
If i aupdirection is SM course of discharge, i.e. i aup<0, then carry out Pressure and Control in the following way:
If (a) U asupi/ N aup<U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup<U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup>=U sm, then conducting i-th group of module group, and turn off other module group;
3.3) by N abelowbe converted into binary number, be designated as N nabelow; N nabeloweach from low level to a high position, respectively with the 1st of lower bridge arm module group to N number of module group one_to_one corresponding; According to N nabelowin each numerical value, following control is carried out to each module group:
3.3.1) work as N nabelowwhen having at least 2 to be 1, conducting N nabelowin equal the module group of the position correspondence of 1, turn off other module group and (comprise N nabelowin equal the module group of the position correspondence of 0 and N+1 module group);
3.3.2) work as N nabelowin everybody when being congruent to 0, turn off the lower all module groups of brachium pontis;
3.3.3) work as N nabelowwhen only having 1 to equal 1, other everybody when all equaling 0, if the position equaling 1 is i-th, and under setting this phase the measured value of bridge arm current as i abelow;
If i abelowdirection is SM charging direction, i.e. i abelow>0, then adopt and carry out Pressure and Control as follows:
If (a) U asbelowi/ N abelow>U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asbelowi/ N abelow>U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
(c) U asbelowi/ N abelow≤ U sm, then conducting i-th group of module group, and turn off other module group;
If i abelowdirection is SM course of discharge, i.e. i abelow<0, then carry out Pressure and Control in the following way:
If (a) U asbelowi/ N abelow<U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asbelowi/ N abelow<U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
(c) U asbelowi/ N abelow>=U sm, then conducting i-th group of module group, and turn off other module group.
The mean value of assembly submodule voltage is kept to keep in balance by above Pressure and Control process.
Described step 2.4) in, Proportional coefficient K p=1, integral coefficient K i=100.
As a kind of embodiment of the present invention, described N value is 3, inductance value L is 2.8mH, and capacitance C is 2800uH, DC voltage U dcfor 800V, SM submodule reference voltage U smfor 100V.
The present invention is by 2 of brachium pontis nindividual submodule is according to 2 0, 2 1, 2 2... 2 n-1, 1 is divided into N+1 module group, and in work, often submodule state is consistent in group group, i.e. conducting simultaneously or shutoff.An often group only configuration voltage sensor, for measuring this group magnitude of voltage.Voltage stabilizing control method, voltage recording method, modulator approach and pressure equalizing control method according to this structural design.Voltage stabilizing controls to adopt pi regulator to stablize the capacitance voltage sum of each mutually all submodules; Voltage recording method is used for preserving the magnitude of voltage of each module group; Modulator approach is used for determining the on off operating mode of a module group; Pressure and Control are used for keeping the mean value of assembly submodule voltage to keep in balance.This control strategy adopts the control mode of submodule component group, reduces voltage transformer required in MMC system in a large number, and then reduces the cost of system hardware complexity and reduction MMC, has good engineer applied and is worth.
The invention has the beneficial effects as follows: 1) decrease voltage transformer; 2) cost of system is significantly reduced.
Accompanying drawing explanation
Fig. 1 modular multilevel converter structure schematic diagram;
Brachium pontis submodule grouping schematic diagram in Fig. 2 A phase;
Fig. 3 A phase Pressure and Control block diagram;
The conducting of Fig. 4 the 3rd module group and excision schematic diagram; Fig. 4 (a) is the 3rd module group conducting schematic diagram; Fig. 4 (b) is the 3rd module group excision schematic diagram;
Fig. 5 is that A phase respectively organizes submodule voltage.Wherein Fig. 5 (a) is that upper brachium pontis respectively organizes submodule voltage, and Fig. 5 (b) is that lower brachium pontis respectively organizes submodule voltage;
Fig. 6 A phase exports phase voltage.
Embodiment
In order to make technical problem solved by the invention, technical scheme and beneficial effect clearly understand, below in conjunction with accompanying drawing, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.
Fig. 1 is modular multi-level converter topological structure figure, is made up of three-phase brachium pontis.Every mutually containing upper and lower two brachium pontis, every brachium pontis is containing 2 nindividual identical submodule and a filter inductance L.Submodule is made up of two IGBT and storage capacitors.
Fig. 2 is the schematic diagram of brachium pontis submodule grouping in A phase.In this embodiment, N value is 3, inductance value L is 2.8mH, and capacitance C is 2800uH, DC voltage U dcfor 800V, SM submodule reference voltage U smfor 100V.According to the mode of module grouping, be by 2 n(2 n=8) individual SM submodule is divided into N+1 module group, and the 1st group comprises 2 0individual SM submodule, the 2nd group comprises 2 1individual SM submodule, the 3rd group comprises 2 2individual SM submodule, the 4th group comprises 1 SM submodule.Therefore, brachium pontis submodule is divided into 4 groups, and each group submodule number is followed successively by 1,2,4,1.B, C are similar.
Fig. 3 is A phase voltage stabilizing control block diagram.Suppose that in A phase, brachium pontis is respectively U from first module group to the voltage measuring value of N+1 module group aup1, U aup2, U aup3, U aup4.The lower brachium pontis of A phase is respectively U from first module group to the voltage measuring value of N+1 module group abelow1, U abelow2, U abelow3, U abelow4, then the module group voltage sum U of each conducting of A phase afor:
U a = &Sigma; i = 1 4 U a u p i + &Sigma; i = 1 4 U a b e l o w i
Suppose that measuring the moment has K submodule conducting, then voltage stabilizing controls to be described as:
U aref1＝(U sm-U a/K)(K p+K i/s)
Wherein, K p=1, K i=100, s is integrating factor, U aref1the output that voltage stabilizing controls;
Suppose that MMC current transformer needs the voltage exported to be U aref2, in this embodiment, value is 400sin (100 π t), and t is time variable, timing from MMC conducting time of running.The then modulation voltage U of MMC current transformer areffor: U aref=U aref1+ U aref2;
A phase upper and lower bridge arm conducting number N aupand N abelowbe respectively:
N aup＝round((U dc/2-U aref)/U sm)
N abelow＝round((U dc/2+U aref)/U sm)
Wherein, round () is the function that rounds up;
By N aupbe converted into binary number and obtain N naup; N naupeach from low level to a high position, with the 1st group of upper bridge arm module group to N group one_to_one corresponding respectively;
Work as N naupwhen having at least 2 to be 1, if N naupa certain position be 1, then the corresponding module group of conducting; The modulated process of lower brachium pontis is similar;
B, C phase modulated process and A similar.
Fig. 4 is the 3rd module group conducting and excision schematic diagram.Often submodule state consistency in group group, i.e. conducting simultaneously and shutoff in work.When this group submodule conducting, preserve the voltage measuring value of this module group, until upgrade this record value after this module group conducting next time; To the i-th group of module of brachium pontis in A phase, if its voltage record value is U asupi; To the lower brachium pontis i-th group of module of A phase, voltage record value is U asbelowi.
Work as N nauponly have i-th to be 1, when everybody be all 0 other, Pressure and Control are carried out to the module group corresponding to this; Suppose that the measured value of bridge arm current in A phase is i aup, and i aupdirection is SM charging direction, i.e. i aup>0, then adopt and carry out Pressure and Control as follows:
If (a) U asupi/ N aup>U smand i>1, then conducting the 1 to the i-th-1 module group and N+1 module group, turn off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup>U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup≤ U sm, then conducting i-th group of module group, and turn off other module group;
Suppose that the measured value of bridge arm current in A phase is i aup, and i aupdirection is SM course of discharge, i.e. i aup<0, then carry out Pressure and Control in the following way:
If (a) U asupi/ N aup<U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup<U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup>=U sm, then conducting i-th group of module group, and turn off other module group;
The lower brachium pontis pressure equalizing control method of A phase is similar; B, C pressure equalizing control method is similar with A phase pressure equalizing control method.
Fig. 5 is that A phase respectively organizes submodule voltage.Wherein Fig. 5 (a) is that upper brachium pontis respectively organizes submodule voltage, and Fig. 5 (b) is that lower brachium pontis respectively organizes submodule voltage.As can be seen from the figure, each submodule capacitor voltage of upper brachium pontis is stabilized in 100V, and ripple is 1.5V, meets engine request.This also demonstrates the Pressure and Control strategy validity that the present invention proposes.
Fig. 6 is A phase output voltage, fundamental voltage output of voltage amplitude 400V, and total harmonic distortion is 4.4%, and ripple is 3V, engineering demands, proves the validity of the control strategy that the present invention proposes.

Claims (3)

1. a control method for modularization multi-level converter, is characterized in that,
Described modularization multi-level converter adopts three-phase six bridge arm topological structure, and often comprise upper and lower two brachium pontis mutually, each brachium pontis is by 2 nindividual SM submodule and 1 inductance L are in series, and upper and lower brachium pontis tie point draws phase line; Article three, phase line access public electric wire net; N is integer, wherein, function is for rounding up; U dcfor the DC voltage by converter, U smfor SM submodule reference voltage;
Each SM submodule is a half-bridge current transformer, is made up of two IGBT pipe T1 and T2, two diode D1 and D2 and electric capacity C; Wherein, the emitter of IGBT pipe T1 is connected with the collector electrode of IGBT pipe T2 and forms the anode of SM, and the collector electrode of IGBT pipe T1 is connected with the positive pole of electric capacity C, and the emitter of IGBT pipe T2 is connected with the negative pole of electric capacity and forms the negative terminal of SM; D1 and T1 reverse parallel connection, D2 and T2 reverse parallel connection; The gate pole of IGBT pipe T1 and T2 all receives control wave;
Often go up 2 of brachium pontis mutually nindividual SM submodule and 1 inductance L are connected successively, and the anode namely going up brachium pontis first SM submodule is connected with DC side positive pole; The anode of i-th the SM submodule mediated is connected with the negative terminal of the i-th-1 SM submodule, and the negative terminal of i-th SM submodule is connected with the anode of the i-th+1 SM submodule, i=2, and 3 ..., 2 n-1; Upper brachium pontis the 2nd nthe negative terminal of individual SM submodule is connected with inductance L one end, and the inductance L other end draws phase line;
Every inductance L and 2 descending brachium pontis mutually nindividual SM submodule is connected successively, and namely phase line is drawn in inductance L one end, and the inductance L other end is connected with the anode of lower brachium pontis first SM submodule; The anode of i-th the SM submodule mediated is connected with the negative terminal of the i-th-1 SM submodule, i-th SM submodule negative terminal be connected with the anode of the i-th+1 SM submodule, i=2,3 ..., 2 n-1; Lower brachium pontis the 2nd nthe negative terminal of individual SM submodule is connected with DC side negative pole;
The neutral earthing of DC side power supply;
For the arbitrary phase in three-phase (A phase, B phase and C phase), described control method comprises the following steps:
Step 1, module are divided into groups;
Step 2, voltage stabilizing control, and adopt pi regulator to stablize the capacitance voltage sum of each mutually all submodules;
Step 3, modulation, be used for determining the on off operating mode of a module group;
The module grouping of described step 1, specifically comprises the following steps:
By 2 of each for converter brachium pontis nindividual SM submodule is divided into N+1 module group, and front N group respectively comprises 2 i-1individual SM submodule, i is the sequence number of module group, i=1,2 ..., (namely the 1st group comprises 2 to N 0individual SM submodule, the 2nd group comprises 2 1individual SM submodule, the 3rd group comprises 2 2individual SM submodule, the like, N group comprises 2 n-1individual SM submodule), N+1 group comprises 1 SM submodule; Each module group voltage sensor in parallel, for measuring the total voltage of SM submodule electric capacity in this module group; In work, often submodule state is consistent in group group, i.e. conducting simultaneously or shutoff;
The voltage stabilizing of described step 2 controls, and specifically comprises the following steps:
2.1) measure brachium pontis in this phase and, from first module group to the magnitude of voltage of N+1 module group, voltage measuring value is designated as U respectively aup1, U aup2...., U aupi...., U aup (N+1); Under measuring this phase, brachium pontis is from first module group to the magnitude of voltage of N+1 module group, and voltage measuring value is designated as U respectively abelow1, U abelow2..., U abelowi...., U abelow (N+1);
2.2) for N+1 module group of each brachium pontis, when certain module group is in conducting state, the voltage measuring value of this module group is preserved; To i-th the module group of brachium pontis in this phase, its voltage measuring value is saved as voltage record value U asupi; To i-th the module group of brachium pontis under this phase, its voltage measuring value is recorded as U asbelowi; Until upgrade this voltage record value after this module group conducting next time;
2.3) according to step 2.1) voltage measuring value that obtains calculates the voltage sum U of this mutually each module group afor:
U a = &Sigma; i = 1 N + 1 U a u p i + &Sigma; i = 1 N + 1 U a b e l o w i
2.4) the measurement moment is established to have the conducting of K module group, according to the output U that following formulae discovery voltage stabilizing controls aref1:
U aref1＝(U sm-U a/K)(K p+K i/s)
Wherein, K pfor proportionality coefficient, K ifor integral coefficient, 1/s is that (integrating factor is to (U to integrating factor sm-U a/ K) carry out integration, namely As time goes on, ceaselessly this error amount cumulative);
2.5) converter is set to need the voltage of output as U aref2, according to the modulation voltage U of following formulae discovery converter aref:
U aref＝U aref1+U aref2；
The modulation of described step 3, specifically comprises the following steps:
3.1) according to step 2.5) calculate modulation voltage U aref, calculate the conducting number N of brachium pontis and lower bridge arm module group in this phase respectively aupand N abelow:
N aup＝round((U dc/2-U aref)/U sm)
N abelow＝round((U dc/2+U aref)/U sm)
Wherein, round () is the function that rounds up;
3.2) by N aupbe converted into binary number, be designated as N naup; N naupeach from low level to a high position, respectively with upper brachium pontis the 1st to N number of module group one_to_one corresponding; According to N naupin each numerical value, following control is carried out to each module group:
3.2.1) work as N naupin when having at least 2 to equal 1, conducting N naupin equal the module group of the position correspondence of 1, turn off other module group and (comprise N naupin equal the module group of the position correspondence of 0 and N+1 module group);
3.2.2) work as N naupin everybody when being congruent to 0, all module groups of brachium pontis in shutoff;
3.2.3) work as N naupwhen only having 1 to equal 1, other everybody when all equaling 0, if the position equaling 1 is i-th, and set the measured value of bridge arm current in this phase as i aup;
If i aupdirection is SM charging direction, i.e. i aup>0, then adopt and carry out Pressure and Control as follows:
If (a) U asupi/ N aup>U smand i>1, then conducting the 1 to the i-th-1 module group and N+1 module group, turn off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup>U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup≤ U sm, then conducting i-th group of module group, and turn off other module group;
If i aupdirection is SM course of discharge, i.e. i aup<0, then carry out Pressure and Control in the following way:
If (a) U asupi/ N aup<U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asupi/ N aup<U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
If (c) U asupi/ N aup>=U sm, then conducting i-th group of module group, and turn off other module group;
3.3) by N abelowbe converted into binary number, be designated as N nabelow; N nabeloweach from low level to a high position, respectively with the 1st of lower bridge arm module group to N number of module group one_to_one corresponding; According to N nabelowin each numerical value, following control is carried out to each module group:
3.3.1) work as N nabelowwhen having at least 2 to be 1, conducting N nabelowin equal the module group of the position correspondence of 1, turn off other module group and (comprise N nabelowin equal the module group of the position correspondence of 0 and N+1 module group);
3.3.2) work as N nabelowin everybody when being congruent to 0, turn off the lower all module groups of brachium pontis;
3.3.3) work as N nabelowwhen only having 1 to equal 1, other everybody when all equaling 0, if the position equaling 1 is i-th, and under setting this phase the measured value of bridge arm current as i abelow;
If i abelowdirection is SM charging direction, i.e. i abelow>0, then adopt and carry out Pressure and Control as follows:
If (a) U asbelowi/ N abelow>U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asbelowi/ N abelow>U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
(c) U asbelowi/ N abelow≤ U sm, then conducting i-th group of module group, and turn off other module group;
If i abelowdirection is SM course of discharge, i.e. i abelow<0, then carry out Pressure and Control in the following way:
If (a) U asbelowi/ N abelow<U smand i>1, then conducting the 1st group is to the i-th-1 group and N+1 module group, turns off other module group (namely i-th to N number of module group);
If (b) U asbelowi/ N abelow<U smand i=1, then conducting N+1 group module group, turn off other module group (namely the 1st to N number of module group);
(c) U asbelowi/ N abelow>=U sm, then conducting i-th group of module group, and turn off other module group.
2. the control method of modularization multi-level converter according to claim 1, is characterized in that, described step 2.4) in, Proportional coefficient K p=1, integral coefficient K i=100.
3. the control method of modularization multi-level converter according to claim 1, is characterized in that, described N value is 3, inductance value L is 2.8mH, and capacitance C is 2800uH, DC voltage U dcfor 800V, SM submodule reference voltage U smfor 100V.
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