CN106787884B - The pressure modulator approach and press modulating device that nearest level approaches - Google Patents

The pressure modulator approach and press modulating device that nearest level approaches Download PDF

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Publication number
CN106787884B
CN106787884B CN201710054263.4A CN201710054263A CN106787884B CN 106787884 B CN106787884 B CN 106787884B CN 201710054263 A CN201710054263 A CN 201710054263A CN 106787884 B CN106787884 B CN 106787884B
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submodule
bridge arm
diff
voltage
capacitance voltage
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CN106787884A (en
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刘韬
于向恩
李东松
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TBEA Xinjiang Sunoasis Co Ltd
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TBEA Xinjiang Sunoasis Co Ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion 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
    • H02M7/483Converters with outputs that each can have more than two voltages levels
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion 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
    • H02M7/483Converters with outputs that each can have more than two voltages levels
    • H02M7/4835Converters 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

Abstract

The present invention provides a kind of pressure modulator approach that nearest level approaches, comprising: the default unbalanced degree h of submodule, if bridge arm current iarmDirection be positive, then control the switching of the bridge arm Neutron module so that the difference of capacitance voltage minimum value is less than h*U in capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put intoave;If bridge arm current iarmDirection be negative, then control the switching of the bridge arm Neutron module so that the difference of capacitance voltage minimum value is less than h*U in capacitance voltage maximum value and the submodule put into the removed submodule of the bridge armave.Correspondingly, a kind of pressure modulating device is provided.The present invention under the premise of meeting equal pressure request, can reduce the on-off times of power device, reduce switching loss.

Description

The pressure modulator approach and press modulating device that nearest level approaches
Technical field
The present invention relates to flexible T & D Technology fields, and in particular to a kind of pressure modulator approach that nearest level approaches, And a kind of pressure modulating device that nearest level approaches.
Background technique
Compared with the inverter of conventional voltage source, modularization multi-level converter (Modular Multilever Converter, MMC) have many advantages, such as that favorable expandability, harmonic wave are small, switching frequency is low, few to the consistent triggering requirement of device, in height It presses application field with the obvious advantage, is particularly suitable for direct current transportation application.Flexible DC transmission technology based on MMC is answered extensively For fields such as new energy submitting, city dilatation, regional power grid interconnection and island power supplies, compared to Traditional DC transmission of electricity skill The advantage of art, flexible DC transmission technology gradually highlights.The country has carried out multinomial flexible DC transmission demonstration project, increasingly More power transmission engineerings uses the flexible DC transmission technology based on MMC, pushes the development of flexible DC transmission technology.
In MMC include a large amount of power device, and for the control of a large amount of power devices be this field technological difficulties it One.The modulation of MMC mainly includes two functions: one, by the investment of submodule and excision, generating according to reference voltage influences electricity The waveform of pressure;Two, the Balance route of module voltage is completed using the charge/discharge characteristics of submodule.Below to the two functions into Row specifically describes.
In the flexible HVDC transmission system based on MMC, the control of valve grade is a very crucial technology, for converter valve The more system of bridge arm number of modules mostly uses nearest level to approach (NLM) method and is modulated.Specifically, by adjusting each bridge The switching of arm Neutron module makes the staircase waveform of output being made of the sum of the voltage of different number submodule approach preset ginseng Voltage waveform is examined, to judge the submodule number that each bridge arm needs to put into or cut off by approaching on waveform.
For MMC, DC side energy storage is to be connected to maintain by multiple submodule capacitance voltage, when energy variation, electricity A degree of fluctuation will necessarily be had by holding voltage;In addition, the size of the loss of the submodule capacitor in the same bridge arm, capacitance The factors such as difference can also make the capacitance voltage of each submodule uneven, influence the normal operation of MMC.It therefore must be to each height Module capacitance voltage carries out Balance route, to guarantee the stable operation of system.
However, needing in traditional Pressure and Control strategy constantly according to the capacitance voltage and bridge arm current after sequence Direction determines the switching situation of each submodule, even if submodule capacitor voltage variation is little, it is also possible to frequent switching conversion, Cause the on-off times of IGBT in each bridge arm more, switching loss is big.
Summary of the invention
The technical problem to be solved by the present invention is to provide a kind of full for the drawbacks described above in the presence of the prior art Foot is under the premise of pressure request, reduces that the on-off times of power device, to reduce approaching based on nearest level for switching loss equal It presses modulator approach and presses modulating device.
Solving technical solution used by present invention problem is:
The present invention provides a kind of pressure modulator approach that nearest level approaches comprising following steps:
The capacitance voltage value and switching state information of all submodules in each bridge arm in each control period are acquired in real time, with And each bridge arm current iarmDirectional information;
Obtain the capacitance present average voltage U of each bridge arm Neutron module in this secondary control periodave, each bridge arm put into Submodule in capacitance voltage maxima and minima and the removed submodule of each bridge arm capacitance voltage maximum value with most Small value;
Calculate in the submodule that each bridge arm has been put into capacitance voltage maximum value and removed submodule capacitance voltage most The difference of small value, and calculate capacitance voltage maximum value and capacitor electricity in the submodule put into each removed submodule of bridge arm Press the difference of minimum value;
The default unbalanced degree h of submodule, if bridge arm current iarmDirection be positive, then control the throwing of the bridge arm Neutron module It cuts so that capacitance voltage minimum value in capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put into Difference be less than h*Uave;If bridge arm current iarmDirection be negative, then control the switching of the bridge arm Neutron module so that the bridge arm The difference of capacitance voltage minimum value is less than h*U in capacitance voltage maximum value and the submodule put into removed submoduleave
The present invention also provides a kind of pressure modulating devices that nearest level approaches comprising:
Acquisition unit, for acquiring the capacitance voltage value and throwing of all submodules in each bridge arm in each control period in real time Cut status information and each bridge arm current iarmDirectional information;
Acquiring unit, for obtaining the capacitance present average voltage U of each bridge arm Neutron module in this secondary control periodave、 Capacitor electricity in capacitance voltage maxima and minima and the removed submodule of each bridge arm in the submodule that each bridge arm has been put into Press maxima and minima;
Computing unit, for calculating capacitance voltage maximum value and removed submodule in the submodule that each bridge arm has been put into The difference of middle capacitance voltage minimum value, and calculate capacitance voltage maximum value and the son put into each removed submodule of bridge arm The difference of capacitance voltage minimum value in module;
Control unit is inside preset with the unbalanced degree h of submodule, in bridge arm current iarmDirection be timing, control The switching of the bridge arm Neutron module is so that capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put into The difference of capacitance voltage minimum value is less than h*U in blockave;And in bridge arm current iarmDirection when being negative, control the bridge arm neutron The switching of module is so that capacitance voltage maximum value and capacitor in the submodule put into are electric in the removed submodule of the bridge arm The difference of minimum value is pressed to be less than h*Uave
The utility model has the advantages that
The pressure modulator approach and pressure modulating device that nearest level of the present invention approaches are applied to flexible DC transmission Unbalanced degree h and bridge arm submodule capacitance present average voltage U when in the MMC of system, according to submoduleave, in bridge arm electricity Flow iarmDirection be timing, control the switching of the bridge arm Neutron module, that is, change the investment state of the bridge arm Neutron module and cut Except state, guarantee that capacitance voltage is minimum in capacitance voltage maximum value and removed submodule in submodule that the bridge arm has been put into The difference of value is less than h*Uave;In bridge arm current iarmDirection when being negative, control the switching of the bridge arm Neutron module, that is, change the bridge The investment state of arm Neutron module and excision state, guarantee in the removed submodule of the bridge arm capacitance voltage maximum value and have thrown The difference of capacitance voltage minimum value is less than h*U in the submodule enteredave, thus meeting flexible direct-current transmission valve control system sub-modules On the basis of pressing, the switching frequency of submodule is reduced, the switching loss of power device in submodule (such as IGBT) is reduced, Directly enhance power transmission efficiency.
Detailed description of the invention
Fig. 1 is the topological diagram of MMC in flexible HVDC transmission system applied by the present invention;
Fig. 2 is the flow chart for pressing modulator approach that a kind of nearest level that the embodiment of the present invention 1 provides approaches;
Fig. 3 is the flow chart for pressing modulator approach that another nearest level that the embodiment of the present invention 1 provides approaches;
Fig. 4 is the schematic diagram for pressing modulating device that the nearest level that the embodiment of the present invention 2 provides approaches;
Fig. 5 is the structural schematic diagram of control unit in Fig. 4;
Fig. 6 is the waveform of each submodule capacitor voltage in bridge arm in the A phase provided by the invention obtained through PSCAD emulation Figure.
In figure: SM- submodule;100- acquisition unit;200- acquiring unit;300- computing unit;400- control is single Member;The first comprising modules of 401-;The first searching module of 402-;The first switching module of 403-;The second comprising modules of 404-; The second searching module of 405-;The second switching module of 406-;The first sequencing unit of 500-;The second sequencing unit of 600-.
Specific embodiment
Technical solution in order to enable those skilled in the art to better understand the present invention, with reference to the accompanying drawings and examples to this Invention is described in further detail.
Pressure modulator approach of the present invention and pressure modulating device can be applied to flexible HVDC transmission system, wherein MMC The topological structure of (modularization multi-level converter) is detailed in Fig. 1.As shown in Figure 1, MMC includes three phase elements, respectively A phase is single Member, B phase element and C phase element, each phase element include upper bridge arm and lower bridge arm, amount to 6 bridge arms.The structure of each bridge arm It is identical, it include the reactor and N number of submodule SM being sequentially connected in series.Due to containing power device in submodule, can also claim For power module.
The quantity of the submodule of each phase element is at the beginning of being designed by system by DC bus-bar voltage, electronic device pressure resistance What the factors such as grade and the type of submodule codetermined.In the present embodiment, the quantity 2N=of the submodule of each phase element Udc/USM, wherein UdcIt is the voltage between positive and negative direct current bus, USMIt is the capacitance voltage of each submodule, N is in each bridge arm The quantity of submodule, and N > 1.
Specifically, as shown in Figure 1, upper bridge arm for A phase element, ac output end A are sequentially connected reactor, N number of son The positive Vdc+ of DC bus-bar voltage is accessed after module SM, wherein submodule SM1Output terminals A 1 and DC bus-bar voltage just Pole Vdc+ connection, output end B1 and adjacent submodule SM2Output terminals A 2 connect, submodule SMNOutput terminals A n and adjacent Submodule SM(N-1)Output end B (n-1) connection, submodule SMNOutput end Bn and reactor one end connect, reactor The other end exchanges output terminals A with A phase and connect, other submodules of the upper bridge arm of A phase element (remove submodule SM1With submodule SMN Submodule in addition) output terminals A i previous submodule adjacent thereto output end B (i-1) connection, A phase element it is upper The output terminals A (i+1) of the latter submodule output end Bi of other submodules of bridge arm adjacent thereto connects, and 2≤i≤ (N-1).Here, the previous submodule adjacent with a certain submodule refers to adjacent with the submodule and in circuit connecting relation On than the submodule closer to DC bus-bar voltage positive Vdc+ submodule, such as submodule SM2It is and submodule SM3Phase Adjacent previous submodule;The latter submodule adjacent with a certain submodule refers to adjacent with the submodule and connects in circuit Connect the submodule for exchanging output terminals A in relationship closer to A phase than the submodule, such as submodule SM3It is and submodule SM2It is adjacent The latter submodule.As shown in Figure 1, bridge arm current i on A phase elementarmDirection it is downward when be defined as positive direction, work as bridge arm Current direction is positive (iarm> 0) certainly, removed in the bridge arm to the capacitor charging for the submodule that upper bridge arm has been put into when The capacitor of submodule not charges;Conversely, upper bridge arm current iarmDirection it is upward when be defined as negative direction, when bridge arm current side To (the i that is negativearm< 0) it when, discharges to the capacitor for the submodule that upper bridge arm has been put into, certainly, removed submodule in the bridge arm Capacitor not discharge.
As for the lower bridge arm of A phase element, the difference of structure and the structure of the upper bridge arm of A phase element is only that, is exchanged defeated Outlet A is sequentially connected the cathode Vdc- of access DC bus-bar voltage after reactor, N number of submodule SM.As shown in Figure 1, A phase element Lower bridge arm electric current iarmDirection it is downward when be defined as positive direction, the capacitor charging of the submodule put at this time to lower bridge arm, instead It, lower bridge arm electric current iarmDirection it is upward when be defined as negative direction, the capacitor of the submodule put at this time to lower bridge arm is put Electricity.
And the structure of the upper and lower bridge arm of B phase element and C phase element can be respectively with reference to the knot of the upper and lower bridge arm of A phase element Structure, details are not described herein again.As can be seen that the structure of the upper bridge arm of each phase element and the symmetrical configuration of lower bridge arm.
In the present embodiment, the structure of each submodule is all the same, is half-bridge submodule comprising transistor VT1 and with Diode VD1, the transistor VT2 of its reverse parallel connection and diode VD2 and capacitor C with its reverse parallel connection.
Below with submodule SM1Structure for be described in detail half-bridge submodule specific structure.
The collector of transistor VT1 is connect with the cathode of diode VD1, emitter and the positive of diode VD1 connect, brilliant The collector of body pipe VT2 is connect with the cathode of diode VD2, emitter and the positive of diode VD2 connect, transistor VT1's Emitter is also connect with the collector of transistor VT2, and output terminals A 1 and the emitter of transistor VT1 and the collection of transistor VT2 The tie point of electrode is connected;The anode of capacitor C is connected with the collector of transistor VT1, and the cathode of capacitor C is with transistor VT2's Emitter is connected.
In the embodiment of the present invention, the power device in each submodule can use IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor), MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, Metal-Oxide Semiconductor field effect transistor) or IGCT (Integrated Gate Commutated Thyristors, integrated gate commutated thyristor).
Technical solution of the present invention is described in detail below by specific embodiment 1 and 2.
Embodiment 1:
The present embodiment provides a kind of pressure modulator approaches that nearest level approaches.As shown in Fig. 2, described press modulator approach Include the following steps S101 to S104.
S101. the capacitance voltage value and switching state for acquiring all submodules in each bridge arm in each control period in real time are believed Breath and each bridge arm current iarmDirectional information.
In the present embodiment, bridge arm current iarmDirection it is downward when be positive direction (iarm> 0), i.e. bridge arm current iarmFrom direct current It when the positive Vdc+ of busbar voltage flows to the cathode Vdc- of DC bus-bar voltage is positive direction, at this time to having been put into the bridge arm The capacitor charging of submodule;Conversely, bridge arm current iarmDirection it is upward when be negative direction (iarm< 0) it, gives in the bridge arm at this time The capacitor of the submodule of investment discharges, and occurs so as to cause the unbalanced situation of capacitance voltage of submodule, therefore in this step Acquire bridge arm current iarmDirectional information, and below the step of according to bridge arm current iarmDirection it is positive and negative, as it It is ranked up the standard (hereinafter will be described in detail) pressed afterwards.
S102. the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period is obtainedave, each bridge arm Capacitance voltage maximum value in capacitance voltage maxima and minima and the removed submodule of each bridge arm in the submodule of investment With minimum value.
Specifically, within this secondary control period, according to the capacitor of all submodules in each bridge arm acquired in step s101 Voltage value, so that it may obtain the capacitance present average voltage U of each bridge arm Neutron moduleave;According to acquired in step s101 each The capacitance voltage value and switching state information of all submodules can be obtained by electric in the submodule that each bridge arm has been put into bridge arm Hold capacitance voltage maxima and minima in voltage max and minimum value and the removed submodule of each bridge arm.
S103. capacitance voltage maximum value and capacitor electricity in removed submodule in the submodule that each bridge arm has been put into are calculated The difference of minimum value is pressed, and calculates capacitance voltage maximum value and electricity in the submodule put into each removed submodule of bridge arm Hold the difference of voltage minimum.
S104. the unbalanced degree h of submodule is preset, if bridge arm current iarmDirection be positive (iarm> 0) bridge arm, is then controlled The switching of Neutron module is so that electricity in capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put into The difference for holding voltage minimum is less than h*Uave;If bridge arm current iarmDirection be negative (iarm< 0) the bridge arm Neutron module, is then controlled Switching so that capacitance voltage is most in capacitance voltage maximum value and the submodule put into the removed submodule of the bridge arm The difference of small value is less than h*Uave, to realize pressure modulation.Wherein, the unbalanced degree h of submodule should be permitted in flexible HVDC transmission system Can in the range of, can specifically be set according to the actual situation by those skilled in the art.
It, can be according to bridge arm current i when the quantity of bridge arm investment submodule changes in this steparmSide To capacitance voltage is minimum or the highest submodule of capacitance voltage for investment or excision, will be detailed below.
Further, after step slol, before step S104 further include following steps:
The submodule put into each bridge arm in this secondary control period is ranked up by capacitance voltage from big to small respectively, To obtain the corresponding investment state submodule sorted lists of each bridge arm, including m submodule;And to this secondary control week Removed submodule is ranked up by capacitance voltage from big to small respectively in each bridge arm in phase, and to obtain, each bridge arm is corresponding to be cut Except state submodule sorted lists, including n submodule, and m+n=N, m, n and N are integer, and N is each bridge arm packet The submodule number included;
Obtain the conducting number Non (k) of each bridge arm Neutron module and each bridge arm in the last control period in this secondary control period The conducting number Non (k-1) of Neutron module, wherein k is the integer greater than 1.
Then step S104 specifically comprises the following steps S104-1 to S104-7.
S104-1. the unbalanced degree h of submodule is preset.
S104-2. as bridge arm current iarmDirection be positive (iarm> 0) when, by the corresponding investment state submodule of the bridge arm N submodule in m submodule and excision state submodule sorted lists in sorted lists sequentially forms first Sorted lists are first handled the submodule submodule of investment state (be in) of bridge arm investment, according to voltage by Small sequence is arrived greatly to be ranked up, then the submodule (being in the submodule of excision state) of bridge arm excision is handled, It is ranked up also according to the descending sequence of voltage, to complete the sequence to the N number of submodule of the bridge arm, wherein the m The capacitance voltage of submodule is U from big to small1To Um, the capacitance voltage of the n submodule is U from big to smallm+1To UN, thus Difference according to bridge arm current direction is ranked up the submodule in the bridge arm.
S104-3. first sorted lists are directed to, U is calculatedi-UN-i+1, i is incremented by since 1, and i is integer, and successively With h*UaveIt is compared, meets U until findingi-UN-i+1<h*UaveI value, to obtain the son for needing to carry out bridge arm voltage equilibrium Number of modules.
S104-4. the switching of the bridge arm Neutron module is controlled according to the i value that finds, Non (k) and Non (k-1), so that The difference of capacitance voltage minimum value is less than in capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put into h*Uave
In this step, after having obtained needing to carry out the submodule number i of bridge arm voltage equilibrium, in conjunction with Non (k) and Non (k-1) switching for controlling corresponding submodule in the bridge arm can realize the electric voltage equalization of submodule.For example, working as bridge arm current most When big, change the submodule of switching state if necessary, it can will be in excision state and the minimum submodule of capacitance voltage Investment, to meet system needs, therefore in order to determine the submodule for finally needing to change switching state, need to Non (k) with The different situations of the difference of Non (k-1) are judged, are described in more detail below.
S104-5. as bridge arm current iarmDirection be negative (iarm< 0) when, by the corresponding excision state submodule of the bridge arm M submodule in n submodule and investment state submodule sorted lists in sorted lists sequentially forms second Sorted lists are first handled the submodule submodule of excision state (be in) of bridge arm excision, according to voltage by Small sequence is arrived greatly to be ranked up, then the submodule (being in the submodule of investment state) of bridge arm investment is handled, It is ranked up also according to the descending sequence of voltage, to complete the sequence to the N number of submodule of the bridge arm, wherein the n The capacitance voltage of submodule is U from big to small1To Un, the capacitance voltage of the m submodule is U from big to smalln+1To UN, thus Difference according to bridge arm current direction is ranked up the submodule in the bridge arm.
S104-6. second sorted lists are directed to, U is calculatedj-UN-j+1, j is incremented by since 1, and j is integer, and successively With h*UaveIt is compared, meets U until findingj-UN-j+1<h*UaveJ value, to obtain the submodule for needing to carry out electric voltage equalization Number.
S104-7. the switching of the bridge arm Neutron module is controlled according to the j value that finds, Non (k) and Non (k-1), so that The difference of capacitance voltage minimum value is less than in capacitance voltage maximum value and the submodule put into the removed submodule of the bridge arm h*Uave
In this step, after having obtained needing to carry out the submodule number j of bridge arm voltage equilibrium, in conjunction with Non (k) and Non (k-1) switching for controlling corresponding submodule in the bridge arm can realize the electric voltage equalization of submodule.And it is finally needed to determine The submodule for changing switching state needs the different situations of the difference to Non (k) and Non (k-1) to judge, hereinafter will Detailed description.
Further, after step slol, before step S104 further include following steps:
Calculated the difference N of the quantity of each this secondary control of bridge arm period and investment submodule of upper secondary control perioddiff=Non (k)- Non (k-1), so that this clear secondary control period and upper secondary control period put into son to meet brought by pre-set output voltage The difference of module number;And obtain the excision number Noff (k) of each bridge arm Neutron module in this secondary control period.
Then the step S104-4 includes the following steps A and B.
A. as bridge arm current iarmDirection be timing, according to find i value, Ndiff, Non (k) and Noff (k) are obtained should The corresponding first additional adjustment number of modules N of bridge armBAN1.Wherein, NdiffAlternatively referred to as this secondary control period and upper secondary control period Submodule conducting variation number, particularly may be divided into three kinds of situations: Ndiff> 0, Ndiff=0 and Ndiff<0。
Specifically, if Ndiff=0, the switching state for changing submodule because of voltage modulated is not needed, then NBAN1=Min (i,Non(k),Noff(k));If Ndiff> 0, i.e. output voltage changes, then NBAN1=Min (i, Non (k), Noff (k)- Ndiff);If Ndiff< 0, i.e. output voltage changes, then NBAN1=Min (i, Non (k)+Ndiff,Noff(k))。
B. according to NBAN1And NdiffControl the switching of the bridge arm Neutron module.
Specifically, in NBAN1When=Min (i, Non (k), Noff (k)), the minimum value why chosen in these three values is made For NBAN1, it is because of the case where state that will appear the submodule by certain investments or excision changes, then in bridge arm current iarm Direction be timing, need excision state submodule sorted lists in select the smallest N of voltageBAN1A submodule investment, with And the maximum N of voltage is selected in investment state submodule sorted listsBAN1A submodule excision;
In NBAN1=Min (i, Non (k), Noff (k)-Ndiff) when, in bridge arm current iarmDirection be timing, due to The case where submodule of investment charges theoretically needs to put into the minimum submodule of capacitance voltage, but causes submodule The unbalanced main cause of capacitance voltage is that the capacitance voltage of the submodule of investment is excessively high, so realizing that the core pressed is will be electric Press through high NBAN1A submodule excision, while in order to meet the needs of output predeterminated voltage, it should be by additional NdiffA submodule Investment, i.e. investment (NBAN1+Ndiff) a submodule, it is therefore desirable to selection voltage is minimum in excision state submodule sorted lists (NBAN1+Ndiff) a submodule investment, and the maximum N of voltage is selected in investment state submodule sorted listsBAN1Height Module excision;
In NBAN1=Min (i, Non (k)+Ndiff, Noff (k)) when, in bridge arm current iarmDirection be timing, need The smallest N of voltage is selected in excision state submodule sorted listsBAN1A submodule investment, and in investment state submodule row Maximum (the N of voltage is selected in sequence tableBAN1-Ndiff) excision of a submodule.
The step S104-7 includes the following steps C and D.
C. as bridge arm current iarmDirection when being negative, according to find j value, Ndiff, Non (k) and Noff (k) are obtained should The corresponding second additional adjustment number of modules N of bridge armBAN2.Wherein, NdiffAlternatively referred to as this secondary control period and upper secondary control period Submodule conducting variation number, particularly may be divided into three kinds of situations: Ndiff> 0, Ndiff=0 and Ndiff<0。
Specifically, if Ndiff=0, the switching state for changing submodule because of voltage modulated is not needed, then NBAN2=Min (j,Non(k),Noff(k));If Ndiff> 0, i.e. output voltage changes, then NBAN2=Min (j, Non (k), Noff (k)- Ndiff);If Ndiff< 0, i.e. output voltage changes, then NBAN2=Min (j, Non (k)+Ndiff,Noff(k))。
D. according to NBAN2And NdiffControl the switching of the bridge arm Neutron module.
Specifically, in NBAN2When=Min (j, Non (k), Noff (k)), the minimum value why chosen in these three values is made For NBAN2, it is because of the case where state that will appear the submodule by certain investments or excision changes, then in bridge arm current iarm Direction when being negative, need to select the maximum N of voltage in excision state submodule sorted listsBAN2A submodule investment, with And the smallest N of voltage is selected in investment state submodule sorted listsBAN2A submodule excision;
In NBAN2=Min (j, Non (k), Noff (k)-Ndiff) when, in bridge arm current iarmDirection when being negative, need Maximum (the N of voltage is selected in excision state submodule sorted listsBAN2+Ndiff) a submodule investment, and in investment state subgroup The smallest N of voltage is selected in module sorted listsBAN2A submodule excision;
In NBAN2=Min (j, Non (k)+Ndiff, Noff (k)) when, in bridge arm current iarmDirection when being negative, need The maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, and in investment state submodule row The smallest (the N of voltage is selected in sequence tableBAN2-Ndiff) excision of a submodule.
In addition, in practical applications, if the capacitance voltage maximum value U of bridge arm Neutron modulemaxWith capacitance voltage minimum value UminDifference be not more than h*Uave(i.e. Umax-Umin≤h*Uave) when, voltage-sharing is not present, does not need to press submodule Modulation, only the capacitance voltage maximum value U of bridge arm Neutron modulemaxWith capacitance voltage minimum value UminDifference be greater than h*Uave(i.e. Umax-Umin>h*Uave) when, it just needs to carry out submodule pressure modulation.
Therefore, more preferably, the modulator approach after step S101, before step S104 further include following steps:
Obtain the capacitance voltage maximum value U of each bridge arm Neutron module in this secondary control periodmaxWith capacitance voltage minimum value Umin;Calculate the capacitance voltage maximum value U of each bridge arm Neutron modulemaxWith capacitance voltage minimum value UminDifference.
The step S104 further includes following steps: if the capacitance voltage maximum value U of bridge arm Neutron modulemaxWith capacitor electricity Press minimum value UminDifference be greater than h*Uave, then execute control the bridge arm Neutron module switching the step of;Otherwise, not to the bridge arm Make pressure to handle.
The present embodiment also provides a kind of pressure modulator approach more approached in detail based on nearest level.As shown in figure 3, The pressure modulator approach includes the following steps S201 to S226.
S201. the capacitance voltage value and switching state for acquiring all submodules in each bridge arm in each control period in real time are believed Breath and each bridge arm current iarmDirectional information.
S202. the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period is obtainedave, in each bridge arm The capacitance voltage maximum value U of submodulemaxWith capacitance voltage minimum value Umin
S203. the capacitance voltage maximum value U of each bridge arm Neutron module is calculatedmaxWith capacitance voltage minimum value UminDifference, if Umax-Umin>h*Uave, S204 is thened follow the steps, otherwise, terminates pressure modulation.Wherein, h is the unbalanced degree of preset submodule.
S204. the conducting number Non (k) of each bridge arm Neutron module and excision number Noff (k) in this secondary control period are obtained, with And the last conducting number Non (k-1) for controlling each bridge arm Neutron module in the period.Wherein k is the integer greater than 1.
S205. the difference N of the quantity of each this secondary control of bridge arm period and investment submodule of upper secondary control period was calculateddiff= Non(k)-Non(k-1)。
S206. the submodule put into each bridge arm in this secondary control period is carried out by capacitance voltage from big to small respectively Sequence, to obtain the corresponding investment state submodule sorted lists of each bridge arm, including m submodule.
S207. removed submodule in each bridge arm in this secondary control period is carried out by capacitance voltage from big to small respectively Sequence, to obtain the corresponding excision state submodule sorted lists of each bridge arm, including n submodule.
In step S206 and S207, m+n=N, m, n and N are integer, and N is the submodule number that each bridge arm includes.
S208. judge bridge arm current iarmDirection, if bridge arm current iarmDirection be positive (i.e. iarm> 0) step, is then executed Rapid S209;If bridge arm current iarmDirection be negative (i.e. iarm< 0) S218, is thened follow the steps.
S209. by the m submodule and excision state submodule in the corresponding investment state submodule sorted lists of the bridge arm N submodule in block sequencing list sequentially forms the first sorted lists, wherein the capacitance voltage of the m submodule It is from big to small U1To Um, the capacitance voltage of the n submodule is U from big to smallm+1To UN
S210. first sorted lists are directed to, U is calculatedi-UN-i+1, i is incremented by since 1, and i is integer, and successively with h*UaveIt is compared, meets U until findingi-UN-i+1<h*UaveI value.
S211. judge NdiffValue, if Ndiff=0, then follow the steps S212;If Ndiff> 0, then follow the steps S214;If Ndiff< 0, then follow the steps S216.
S212. N is enabledBAN1=Min (i, Non (k), Noff (k)).
S213. the smallest N of voltage is selected in excision state submodule sorted listsBAN1A submodule investment, Yi Ji The maximum N of voltage is selected in investment state submodule sorted listsBAN1A submodule excision.
S214. N is enabledBAN1=Min (i, Non (k), Noff (k)-Ndiff)。
S215. the smallest (the N of voltage is selected in excision state submodule sorted listsBAN1+Ndiff) a submodule investment, And the maximum N of voltage is selected in investment state submodule sorted listsBAN1A submodule excision.
S216. N is enabledBAN1=Min (i, Non (k)+Ndiff,Noff(k))。
S217. the smallest N of voltage is selected in excision state submodule sorted listsBAN1A submodule investment, Yi Ji Maximum (the N of voltage is selected in investment state submodule sorted listsBAN1-Ndiff) excision of a submodule.
S218. by the n submodule and investment state submodule in the corresponding excision state submodule sorted lists of the bridge arm M submodule in block sequencing list sequentially forms the second sorted lists, wherein the capacitance voltage of the n submodule It is from big to small U1To Un, the capacitance voltage of the m submodule is U from big to smalln+1To UN
S219. second sorted lists are directed to, U is calculatedj-UN-j+1, j is incremented by since 1, and j is integer, and successively with h*UaveIt is compared, meets U until findingj-UN-j+1<h*UaveJ value.
S220. judge NdiffValue, if Ndiff=0, then follow the steps S221;If Ndiff> 0, then follow the steps S223;If Ndiff< 0, then follow the steps S225.
S221. N is enabledBAN2=Min (j, Non (k), Noff (k)).
S222. the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, Yi Ji The smallest N of voltage is selected in investment state submodule sorted listsBAN2A submodule excision.
S223. N is enabledBAN2=Min (j, Non (k), Noff (k)-Ndiff)。
S224. maximum (the N of voltage is selected in excision state submodule sorted listsBAN2+Ndiff) a submodule investment, And the smallest N of voltage is selected in investment state submodule sorted listsBAN2A submodule excision.
S225. N is enabledBAN2=Min (j, Non (k)+Ndiff,Noff(k))。
S226. the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, Yi Ji The smallest (the N of voltage is selected in investment state submodule sorted listsBAN2-Ndiff) excision of a submodule.
It should be noted that above two press in modulator approach, the sequence of steps involved is simply to illustrate that this hair Bright and two kinds of specific examples proposing, without limitation to the sequences of above-mentioned steps, those skilled in the art are actually answering the present invention It can be adjusted on demand in.
In the process of implementation, the task of modulated terminal is mainly executed by bridge arm controller two kinds of modulator approaches of the present embodiment, It includes two that it, which is acted on:
First is that the needs according to system voltage output, in investment of each control period or cut off corresponding submodule and (pass through Corresponding control signal is exported to the power device of submodule to realize) so that electricity of the system output by different number submodule The staircase waveform for holding the sum of voltage composition approaches preset reference voltage waveform;In order to realize the effect, it is also necessary to by bridge arm control Device processed pre-generates the submodule number that each bridge arm should be put into, and specifically, bridge arm controller receives upper level order in advance, according to The switching state information of all submodules obtains each bridge in this secondary control period in each bridge arm that each control period acquires in real time The conducting number Non (k) of the arm Neutron module and last conducting number Non (k-1) for controlling each bridge arm Neutron module in the period;
Second is that realizing the pressure algorithm of submodule inside each bridge arm, specific algorithm is referring to above-described embodiment.
Embodiment 2:
The present embodiment provides a kind of pressure modulating devices that nearest level approaches.As shown in figure 4, described press modulating device Including acquisition unit 100, acquiring unit 200, computing unit 300 and control unit 400.
Wherein, acquisition unit 100 is used to acquire the capacitor electricity of all submodules in each bridge arm in each control period in real time Pressure value and switching state information and each bridge arm current iarmDirectional information;
Acquiring unit 200 is used to obtain the capacitance present average voltage of each bridge arm Neutron module in this secondary control period Uave, electricity in capacitance voltage maxima and minima and the removed submodule of each bridge arm in the submodule that has put into of each bridge arm Hold voltage max and minimum value;
Computing unit 300 is for calculating capacitance voltage maximum value and removed submodule in the submodule that each bridge arm has been put into The difference of capacitance voltage minimum value in block, and calculate capacitance voltage maximum value in each removed submodule of bridge arm and put into The difference of capacitance voltage minimum value in submodule;
The unbalanced degree h of submodule is preset in control unit 400, in bridge arm current iarmDirection be timing, control The switching of the bridge arm Neutron module is so that capacitance voltage maximum value and removed submodule in the submodule that the bridge arm has been put into The difference of capacitance voltage minimum value is less than h*U in blockave;And in bridge arm current iarmDirection when being negative, control the bridge arm neutron The switching of module is so that capacitance voltage maximum value and capacitor in the submodule put into are electric in the removed submodule of the bridge arm The difference of minimum value is pressed to be less than h*Uave
As shown in figure 4, the pressure modulating device further includes the first sequencing unit 500 and the second sequencing unit 600.
Wherein, the first sequencing unit 500 for pressing the submodule put into each bridge arm in this secondary control period respectively Capacitance voltage is ranked up from big to small, to obtain the corresponding investment state submodule sorted lists of each bridge arm, including m Submodule;
Second sequencing unit 600 is used to press removed submodule in each bridge arm in this secondary control period respectively capacitor electricity Pressure is ranked up from big to small, to obtain the corresponding excision state submodule sorted lists of each bridge arm, including n submodule Block, and m+n=N, m, n and N are integer, and N is the submodule number that each bridge arm includes.
Then acquiring unit 200 is also used to obtain in this secondary control period the conducting number Non (k) of each bridge arm Neutron module and upper The conducting number Non (k-1) of each bridge arm Neutron module in a control period, wherein k is the integer greater than 1.
As shown in figure 5, control unit 400 includes:
First comprising modules 401, in bridge arm current iarmDirection be timing, by the corresponding investment state of the bridge arm N submodule in m submodule in submodule sorted lists and excision state submodule sorted lists sequentially group At the first sorted lists, wherein the capacitance voltage of the m submodule is U from big to small1To Um, the capacitor of the n submodule Voltage is U from big to smallm+1To UN
First searching module 402 calculates U for being directed to first sorted listsi-UN-i+1, i is incremented by since 1, and i For integer, and successively with h*UaveIt is compared, meets U until findingi-UN-i+1<h*UaveI value;
First switching module 403, the i value found for basis, Non (k) and Non (k-1) control the bridge arm Neutron module Switching;
Second comprising modules 404, in bridge arm current iarmDirection when being negative, by the corresponding excision state of the bridge arm M submodule in n submodule in submodule sorted lists and investment state submodule sorted lists sequentially group At the second sorted lists, wherein the capacitance voltage of the n submodule is U from big to small1To Un, the capacitor of the m submodule Voltage is U from big to smalln+1To UN
Second searching module 405 calculates U for being directed to second sorted listsj-UN-j+1, j is incremented by since 1, and j For integer, and successively with h*UaveIt is compared, meets U until findingj-UN-j+1<h*UaveJ value;
Second switching module 406, the j value found for basis, Non (k) and Non (k-1) control the bridge arm Neutron module Switching.
Further, computing unit 300 was also used to calculate each this secondary control of bridge arm period and investment of upper secondary control period The difference N of the quantity of modulediff=Non (k)-Non (k-1).
Acquiring unit 200 is also used to obtain the excision number Noff (k) of each bridge arm Neutron module in this secondary control period.
First switching module 403 of control unit is also used in bridge arm current iarmDirection be timing according to the i found Value, Ndiff, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge armBAN1;And according to NBAN1With NdiffControl the switching of the bridge arm Neutron module.
And the first switching module 403 is specifically used for,
In NdiffWhen=0, make NBAN1=Min (i, Non (k), Noff (k)), and in excision state submodule sorted lists Select the smallest N of voltageBAN1A submodule investment, and selection voltage is maximum in investment state submodule sorted lists NBAN1A submodule excision;
In NdiffWhen > 0, make NBAN1=Min (i, Non (k), Noff (k)-Ndiff), and in excision state submodule Sorted list The smallest (the N of voltage is selected in tableBAN1+Ndiff) a submodule investment, and electricity is selected in investment state submodule sorted lists Press maximum NBAN1A submodule excision;
In NdiffWhen < 0, make NBAN1=Min (i, Non (k)+Ndiff, Noff (k)), and in excision state submodule Sorted list The smallest N of voltage is selected in tableBAN1A submodule investment, and selection voltage is maximum in investment state submodule sorted lists (NBAN1-Ndiff) excision of a submodule.
Second switching module 406 of control unit is also used in bridge arm current iarmDirection when being negative according to the j found Value, Ndiff, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge armBAN2;And according to NBAN2With NdiffControl the switching of the bridge arm Neutron module.
And the second switching module 406 is specifically used for,
In NdiffWhen=0, make NBAN2=Min (j, Non (k), Noff (k)), and in NBAN2=Min (j, Non (k), Noff (k)) when, the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, and in investment shape The smallest N of voltage is selected in state submodule sorted listsBAN2A submodule excision;
In NdiffWhen > 0, make NBAN2=Min (j, Non (k), Noff (k)-Ndiff), and in NBAN2=Min (j, Non (k), Noff(k)-Ndiff) when, the maximum (N of voltage is selected in excision state submodule sorted listsBAN2+Ndiff) a submodule throws Enter, and selects the smallest N of voltage in investment state submodule sorted listsBAN2A submodule excision;
In NdiffWhen < 0, make NBAN2=Min (j, Non (k)+Ndiff, Noff (k)), and in NBAN2=Min (j, Non (k)+ Ndiff, Noff (k)) when, the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, and The smallest (the N of voltage is selected in investment state submodule sorted listsBAN2-Ndiff) excision of a submodule.
In addition, the capacitance voltage that acquiring unit 200 is also used to obtain each bridge arm Neutron module in this secondary control period is maximum Value and capacitance voltage minimum value.
Computing unit 300 is also used to, and calculates the capacitance voltage maximum value and capacitance voltage minimum value of each bridge arm Neutron module Difference.
Control unit 400 is also used to big in the capacitance voltage maximum value of bridge arm Neutron module and the difference of capacitance voltage minimum value In h*UaveWhen, control the switching of the bridge arm Neutron module;Otherwise, pressure processing is not made to the bridge arm.
In order to verify the superior function that pressure modulator approach of the present invention is implemented on flexible direct-current transmission field, inventor MMC simulation model has been built using PSCAD, and pressure modulator approach of the present invention is applied to the simulation model, to observe In each bridge arm the case where the switching frequency (switching frequency) and capacitance voltage degree of unbalancedness of each submodule.Specifically it is shown in Table 1.
Table 1
In table 1, P indicates active power, and Q indicates reactive power, and S indicates apparent energy.As it can be seen from table 1 of the invention Modulation algorithm system average frequency of switching can be allowed to maintain within 200Hz, while the unbalanced degree of capacitance voltage of submodule It maintains within 8%.
Meanwhile each submodule capacitor voltage in bridge arm in A phase under systematic steady state full load condition obtained through PSCAD emulation Waveform as shown in fig. 6, from fig. 6 it can be seen that the equalizing effect of the bridge arm submodule is good, even if in Long time scale Interior, the phenomenon that diverging will not occur in the capacitance voltage of submodule, while each submodule of the bridge arm is being pressed in range.
In conclusion the present invention reduces submodule on the basis of meeting flexible direct-current transmission valve control system and pressing Switching frequency reduces the switching loss of power device in submodule (such as IGBT), directly enhances power transmission efficiency.The present invention exists It on the basis of nearest level approximation Strategy, is ranked up by the capacitance voltage to submodule, stringent foundation bridge arm submodule is not Equilibrium degree, judgement need to change the submodule number of switching state, reduce factor module to the full extent and press and bring volume External switch movement.Moreover, not only having met equal pressure request, but also lower under the premise of not increasing existing control system physics framework The frequency of module switching to effectively reduce the switching loss of power device in submodule reduces converter valve water cooling The pressure of system, improves running efficiency of system, enhances system operation reliability, to the industrial application of flexible DC transmission With impetus.
It is understood that the principle that embodiment of above is intended to be merely illustrative of the present and the exemplary implementation that uses Mode, however the present invention is not limited thereto.For those skilled in the art, essence of the invention is not being departed from In the case where mind and essence, various changes and modifications can be made therein, these variations and modifications are also considered as protection scope of the present invention.

Claims (10)

1. a kind of pressure modulator approach that nearest level approaches, which comprises the steps of:
The capacitance voltage value and switching state information of all submodules in each bridge arm in each control period are acquired in real time, and each Bridge arm current iarmDirectional information;
Obtain the capacitance present average voltage U of each bridge arm Neutron module in this secondary control periodave, the son that has put into of each bridge arm Capacitance voltage maximum value and minimum in capacitance voltage maxima and minima and the removed submodule of each bridge arm in module Value;
Calculate capacitance voltage maximum value and capacitance voltage minimum value in removed submodule in the submodule that each bridge arm has been put into Difference, and calculate in each removed submodule of bridge arm capacitance voltage maximum value with capacitance voltage in the submodule put into most The difference of small value;
The default unbalanced degree h of submodule, if bridge arm current iarmDirection be positive, then control the switching of the bridge arm Neutron module with So that in the submodule that the bridge arm has been put into capacitance voltage maximum value and removed submodule capacitance voltage minimum value difference Less than h*Uave;If bridge arm current iarmDirection be negative, then control the switching of the bridge arm Neutron module so that the bridge arm has been cut The difference of capacitance voltage minimum value is less than h*U in capacitance voltage maximum value and the submodule put into the submodule removedave
2. according to claim 1 press modulator approach, which is characterized in that the pressure modulator approach further includes walking as follows It is rapid:
The submodule put into each bridge arm in this secondary control period is ranked up by capacitance voltage from big to small respectively, to obtain The corresponding investment state submodule sorted lists of each bridge arm are taken, including m submodule;And in this secondary control period Removed submodule is ranked up by capacitance voltage from big to small respectively in each bridge arm, to obtain the corresponding excision shape of each bridge arm State submodule sorted lists, including n submodule, and m+n=N, m, n and N are integer, and each bridge arm of N includes Submodule number;
Obtain the conducting number Non (k) of each bridge arm Neutron module and each bridge arm neutron in the last control period in this secondary control period The conducting number Non (k-1) of module, wherein k is the integer greater than 1;
As bridge arm current iarmDirection be timing, it is described control the bridge arm Neutron module switching the step of include:
By the m submodule and excision state submodule sorted lists in the corresponding investment state submodule sorted lists of the bridge arm In n submodule sequentially form the first sorted lists, wherein the capacitance voltage of the m submodule is from big to small U1To Um, the capacitance voltage of the n submodule is U from big to smallm+1To UN
For first sorted lists, U is calculatedi-UN-i+1, i is incremented by since 1, and i is integer, and successively with h*UaveIt carries out Compare, meets U until findingi-UN-i+1<h*UaveI value;
The switching of the bridge arm Neutron module is controlled according to the i value that finds, Non (k) and Non (k-1);
As bridge arm current iarmDirection when being negative, the step of switching for controlling the bridge arm Neutron module includes:
By the n submodule and investment state submodule sorted lists in the corresponding excision state submodule sorted lists of the bridge arm In m submodule sequentially form the second sorted lists, wherein the capacitance voltage of the n submodule is from big to small U1To Un, the capacitance voltage of the m submodule is U from big to smalln+1To UN
For second sorted lists, U is calculatedj-UN-j+1, j is incremented by since 1, and j is integer, and successively with h*UaveIt carries out Compare, meets U until findingj-UN-j+1<h*UaveJ value;
The switching of the bridge arm Neutron module is controlled according to the j value that finds, Non (k) and Non (k-1).
3. according to claim 2 press modulator approach, which is characterized in that
The pressure modulator approach further includes following steps:
Calculated the difference N of the quantity of each this secondary control of bridge arm period and investment submodule of upper secondary control perioddiff=Non (k)-Non (k-1);
Obtain the excision number Noff (k) of each bridge arm Neutron module in this secondary control period;
As bridge arm current iarmDirection be timing, i value that the basis is found, Non (k) and Non (k-1) are controlled in the bridge arm The step of switching of submodule includes:
According to find i value, Ndiff, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge armBAN1
According to NBAN1And NdiffControl the switching of the bridge arm Neutron module;
As bridge arm current iarmDirection when being negative, j value that the basis is found, Non (k) and Non (k-1) are controlled in the bridge arm The step of switching of submodule includes:
According to find j value, Ndiff, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge armBAN2
According to NBAN2And NdiffControl the switching of the bridge arm Neutron module.
4. according to claim 3 press modulator approach, which is characterized in that
I value that the basis is found, Ndiff, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules of the bridge arm NBAN1The step of include:
If Ndiff=0, then NBAN1=Min (i, Non (k), Noff (k));If Ndiff> 0, then NBAN1=Min (i, Non (k), Noff (k)-Ndiff);If Ndiff< 0, then NBAN1=Min (i, Non (k)+Ndiff,Noff(k));
It is described according to NBAN1And NdiffThe step of controlling the switching of the bridge arm Neutron module include:
In NBAN1When=Min (i, Non (k), Noff (k)), selection voltage is the smallest in excision state submodule sorted lists NBAN1A submodule investment, and the maximum N of voltage is selected in investment state submodule sorted listsBAN1A submodule excision;
In NBAN1=Min (i, Non (k), Noff (k)-Ndiff) when, voltage is selected most in excision state submodule sorted lists Small (NBAN1+Ndiff) a submodule investment, and the maximum N of voltage is selected in investment state submodule sorted listsBAN1It is a Submodule excision;
In NBAN1=Min (i, Non (k)+Ndiff, Noff (k)) when, voltage is selected most in excision state submodule sorted lists Small NBAN1A submodule investment, and the maximum (N of voltage is selected in investment state submodule sorted listsBAN1-Ndiff) a Submodule excision;
J value that the basis is found, Ndiff, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules of the bridge arm NBAN2The step of include:
If Ndiff=0, then NBAN2=Min (j, Non (k), Noff (k));If Ndiff> 0, then NBAN2=Min (j, Non (k), Noff (k)-Ndiff);If Ndiff< 0, then NBAN2=Min (j, Non (k)+Ndiff,Noff(k));
It is described according to NBAN2And NdiffThe step of controlling the switching of the bridge arm Neutron module include:
In NBAN2When=Min (j, Non (k), Noff (k)), selection voltage is maximum in excision state submodule sorted lists NBAN2A submodule investment, and the smallest N of voltage is selected in investment state submodule sorted listsBAN2A submodule excision;
In NBAN2=Min (j, Non (k), Noff (k)-Ndiff) when, voltage is selected most in excision state submodule sorted lists Big (NBAN2+Ndiff) a submodule investment, and the smallest N of voltage is selected in investment state submodule sorted listsBAN2It is a Submodule excision;
In NBAN2=Min (j, Non (k)+Ndiff, Noff (k)) when, voltage is selected most in excision state submodule sorted lists Big NBAN2A submodule investment, and the smallest (N of voltage is selected in investment state submodule sorted listsBAN2-Ndiff) a Submodule excision.
5. equal pressure modulator approach described in any one of -4 according to claim 1, which is characterized in that the pressure modulator approach is also Include the following steps:
Obtain the capacitance voltage maximum value and capacitance voltage minimum value of each bridge arm Neutron module in this secondary control period;
Calculate the capacitance voltage maximum value of each bridge arm Neutron module and the difference of capacitance voltage minimum value;
If the capacitance voltage maximum value of bridge arm Neutron module and the difference of capacitance voltage minimum value are greater than h*Uave, then executing control should The step of switching of bridge arm Neutron module;Otherwise, pressure processing is not made to the bridge arm.
6. a kind of pressure modulating device that nearest level approaches characterized by comprising
Acquisition unit, for acquiring the capacitance voltage value and switching shape of all submodules in each bridge arm in each control period in real time State information and each bridge arm current iarmDirectional information;
Acquiring unit, for obtaining the capacitance present average voltage U of each bridge arm Neutron module in this secondary control periodave, each bridge Capacitance voltage is most in capacitance voltage maxima and minima and the removed submodule of each bridge arm in the submodule that arm has been put into Big value and minimum value;
Computing unit, for calculating capacitance voltage maximum value and electricity in removed submodule in the submodule that each bridge arm has been put into Hold the difference of voltage minimum, and calculates capacitance voltage maximum value and the submodule put into each removed submodule of bridge arm The difference of middle capacitance voltage minimum value;
Control unit is inside preset with the unbalanced degree h of submodule, in bridge arm current iarmDirection be timing, control the bridge The switching of arm Neutron module is so that in the submodule that the bridge arm has been put into capacitance voltage maximum value and removed submodule The difference of capacitance voltage minimum value is less than h*Uave;And in bridge arm current iarmDirection when being negative, control the bridge arm Neutron module Switching so that capacitance voltage is most in capacitance voltage maximum value and the submodule put into the removed submodule of the bridge arm The difference of small value is less than h*Uave
7. according to claim 6 press modulating device, which is characterized in that
First sequencing unit, for the submodule put into each bridge arm in this secondary control period respectively by capacitance voltage from big It is ranked up to small, to obtain the corresponding investment state submodule sorted lists of each bridge arm, including m submodule;
Second sequencing unit, for pressing capacitance voltage respectively from big to removed submodule in each bridge arm in this secondary control period It is ranked up to small, to obtain the corresponding excision state submodule sorted lists of each bridge arm, including n submodule, and m+n =N, m, n and N are integer, and N is the submodule number that each bridge arm includes;
The acquiring unit is also used to, and obtains the conducting number Non (k) of each bridge arm Neutron module and last control in this secondary control period The conducting number Non (k-1) of each bridge arm Neutron module in period processed, wherein k is the integer greater than 1;
Described control unit includes:
First comprising modules, in bridge arm current iarmDirection be timing, the corresponding investment state submodule of the bridge arm is arranged N submodule in m submodule and excision state submodule sorted lists in sequence table sequentially forms first row Sequence table, wherein the capacitance voltage of the m submodule is U from big to small1To Um, the capacitance voltage of the n submodule is from big To small for Um+1To UN
First searching module calculates U for being directed to first sorted listsi-UN-i+1, i is incremented by since 1, and i is integer, And successively with h*UaveIt is compared, meets U until findingi-UN-i+1<h*UaveI value;
First switching module, the i value found for basis, Non (k) control the switching of the bridge arm Neutron module with Non (k-1);
Second comprising modules, in bridge arm current iarmDirection when being negative, the corresponding excision state submodule of the bridge arm is arranged M submodule in n submodule and investment state submodule sorted lists in sequence table sequentially forms second row Sequence table, wherein the capacitance voltage of the n submodule is U from big to small1To Un, the capacitance voltage of the m submodule is from big To small for Un+1To UN
Second searching module calculates U for being directed to second sorted listsj-UN-j+1, j is incremented by since 1, and j is integer, And successively with h*UaveIt is compared, meets U until findingj-UN-j+1<h*UaveJ value;
Second switching module, the j value found for basis, Non (k) control the switching of the bridge arm Neutron module with Non (k-1).
8. according to claim 7 press modulating device, which is characterized in that
The computing unit is also used to, calculate each this secondary control of bridge arm period and the upper secondary control period investment submodule quantity it Poor Ndiff=Non (k)-Non (k-1);
The acquiring unit is also used to, and obtains the excision number Noff (k) of each bridge arm Neutron module in this secondary control period;
First switching module of described control unit is also used to, in bridge arm current iarmDirection be timing according to the i value found, Ndiff, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge armBAN1;And according to NBAN1And Ndiff Control the switching of the bridge arm Neutron module;
Second switching module of described control unit is also used to, in bridge arm current iarmDirection when being negative according to the j value found, Ndiff, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge armBAN2;And according to NBAN2And Ndiff Control the switching of the bridge arm Neutron module.
9. according to claim 8 press modulating device, which is characterized in that
First switching module is specifically used for,
In NdiffWhen=0, make NBAN1=Min (i, Non (k), Noff (k)), and selected in excision state submodule sorted lists The smallest N of voltageBAN1A submodule investment, and the maximum N of voltage is selected in investment state submodule sorted listsBAN1It is a Submodule excision;
In NdiffWhen > 0, make NBAN1=Min (i, Non (k), Noff (k)-Ndiff), and in excision state submodule sorted lists Select the smallest (N of voltageBAN1+Ndiff) a submodule investment, and selection voltage is most in investment state submodule sorted lists Big NBAN1A submodule excision;
In NdiffWhen < 0, make NBAN1=Min (i, Non (k)+Ndiff, Noff (k)), and in excision state submodule sorted lists Select the smallest N of voltageBAN1A submodule investment, and selection voltage is maximum in investment state submodule sorted lists (NBAN1-Ndiff) excision of a submodule;
Second switching module is specifically used for,
In NdiffWhen=0, make NBAN2=Min (j, Non (k), Noff (k)), and in NBAN2=Min (j, Non (k), Noff (k)) When, the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, and in investment state subgroup The smallest N of voltage is selected in module sorted listsBAN2A submodule excision;
In NdiffWhen > 0, make NBAN2=Min (j, Non (k), Noff (k)-Ndiff), and in NBAN2=Min (j, Non (k), Noff (k)-Ndiff) when, the maximum (N of voltage is selected in excision state submodule sorted listsBAN2+Ndiff) a submodule investment, with And the smallest N of voltage is selected in investment state submodule sorted listsBAN2A submodule excision;
In NdiffWhen < 0, make NBAN2=Min (j, Non (k)+Ndiff, Noff (k)), and in NBAN2=Min (j, Non (k)+Ndiff, Noff (k)) when, the maximum N of voltage is selected in excision state submodule sorted listsBAN2A submodule investment, and throwing Enter the selection the smallest (N of voltage in state submodule sorted listsBAN2-Ndiff) excision of a submodule.
10. the equal pressure modulating device according to any one of claim 6-9, which is characterized in that
The acquiring unit is also used to, and obtains the capacitance voltage maximum value and capacitor of each bridge arm Neutron module in this secondary control period Voltage minimum;
The computing unit is also used to, calculate each bridge arm Neutron module capacitance voltage maximum value and capacitance voltage minimum value it Difference;
Described control unit is also used to, and is greater than in the capacitance voltage maximum value of bridge arm Neutron module and the difference of capacitance voltage minimum value h*UaveWhen, control the switching of the bridge arm Neutron module;Otherwise, pressure processing is not made to the bridge arm.
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