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 PDFInfo
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 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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Classifications

 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
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 i_{arm}Direction 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 into_{ave}；If bridge arm current i_{arm}Direction 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 arm_{ave}.Correspondingly, a kind of pressure modulating device is provided.The present invention under the premise of meeting equal pressure request, can reduce the onoff times of power device, reduce switching loss.
Description
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 multilevel 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 onoff 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 onoff 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 i_{arm}Directional information；
Obtain the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period_{ave}, 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 i_{arm}Direction 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*U_{ave}；If bridge arm current i_{arm}Direction 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 submodule_{ave}。
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 i_{arm}Directional information；
Acquiring unit, for obtaining the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period_{ave}、
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 i_{arm}Direction 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 block_{ave}；And in bridge arm current i_{arm}Direction 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*U_{ave}。
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 submodule_{ave}, in bridge arm electricity
Flow i_{arm}Direction 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*U_{ave}；In bridge arm current i_{arm}Direction 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 entered_{ave}, thus meeting flexible directcurrent transmission valve control system submodules
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 multilevel 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 busbar 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
U_{dc}/U_{SM}, wherein U_{dc}It is the voltage between positive and negative direct current bus, U_{SM}It 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 busbar voltage is accessed after module SM, wherein submodule SM_{1}Output terminals A 1 and DC busbar voltage just
Pole Vdc+ connection, output end B1 and adjacent submodule SM_{2}Output terminals A 2 connect, submodule SM_{N}Output terminals A n and adjacent
Submodule SM_{(N1)}Output end B (n1) connection, submodule SM_{N}Output 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 SM_{1}With submodule SM_{N}
Submodule in addition) output terminals A i previous submodule adjacent thereto output end B (i1) 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≤
(N1).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 busbar voltage positive Vdc+ submodule, such as submodule SM_{2}It is and submodule SM_{3}Phase
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 SM_{3}It is and submodule SM_{2}It is adjacent
The latter submodule.As shown in Figure 1, bridge arm current i on A phase element_{arm}Direction it is downward when be defined as positive direction, work as bridge arm
Current direction is positive (i_{arm}> 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 i_{arm}Direction it is upward when be defined as negative direction, when bridge arm current side
To (the i that is negative_{arm}< 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 busbar voltage after reactor, N number of submodule SM.As shown in Figure 1, A phase element
Lower bridge arm electric current i_{arm}Direction 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 i_{arm}Direction 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 halfbridge 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 SM_{1}Structure for be described in detail halfbridge 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 (MetalOxideSemiconductor
FieldEffect Transistor, MetalOxide 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 i_{arm}Directional information.
In the present embodiment, bridge arm current i_{arm}Direction it is downward when be positive direction (i_{arm}> 0), i.e. bridge arm current i_{arm}From direct current
It when the positive Vdc+ of busbar voltage flows to the cathode Vdc of DC busbar voltage is positive direction, at this time to having been put into the bridge arm
The capacitor charging of submodule；Conversely, bridge arm current i_{arm}Direction it is upward when be negative direction (i_{arm}< 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 i_{arm}Directional information, and below the step of according to bridge arm current i_{arm}Direction 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 obtained_{ave}, 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 module_{ave}；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 i_{arm}Direction be positive (i_{arm}> 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*U_{ave}；If bridge arm current i_{arm}Direction be negative (i_{arm}< 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*U_{ave}, 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 step_{arm}Side
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 (k1) of Neutron module, wherein k is the integer greater than 1.
Then step S104 specifically comprises the following steps S1041 to S1047.
S1041. the unbalanced degree h of submodule is preset.
S1042. as bridge arm current i_{arm}Direction be positive (i_{arm}> 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 small_{1}To U_{m}, the capacitance voltage of the n submodule is U from big to small_{m+1}To U_{N}, thus
Difference according to bridge arm current direction is ranked up the submodule in the bridge arm.
S1043. first sorted lists are directed to, U is calculated_{i}U_{Ni+1}, i is incremented by since 1, and i is integer, and successively
With h*U_{ave}It is compared, meets U until finding_{i}U_{Ni+1}<h*U_{ave}I value, to obtain the son for needing to carry out bridge arm voltage equilibrium
Number of modules.
S1044. the switching of the bridge arm Neutron module is controlled according to the i value that finds, Non (k) and Non (k1), 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*U_{ave}。
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
(k1) 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 (k1) are judged, are described in more detail below.
S1045. as bridge arm current i_{arm}Direction be negative (i_{arm}< 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 small_{1}To U_{n}, the capacitance voltage of the m submodule is U from big to small_{n+1}To U_{N}, thus
Difference according to bridge arm current direction is ranked up the submodule in the bridge arm.
S1046. second sorted lists are directed to, U is calculated_{j}U_{Nj+1}, j is incremented by since 1, and j is integer, and successively
With h*U_{ave}It is compared, meets U until finding_{j}U_{Nj+1}<h*U_{ave}J value, to obtain the submodule for needing to carry out electric voltage equalization
Number.
S1047. the switching of the bridge arm Neutron module is controlled according to the j value that finds, Non (k) and Non (k1), 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*U_{ave}。
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
(k1) 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 (k1) 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 period_{diff}=Non (k)
Non (k1), so that this clear secondary control period and upper secondary control period put into son to meet brought by preset 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 S1044 includes the following steps A and B.
A. as bridge arm current i_{arm}Direction be timing, according to find i value, N_{diff}, Non (k) and Noff (k) are obtained should
The corresponding first additional adjustment number of modules N of bridge arm_{BAN1}.Wherein, N_{diff}Alternatively 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: N_{diff}> 0, N_{diff}=0 and N_{diff}<0。
Specifically, if N_{diff}=0, the switching state for changing submodule because of voltage modulated is not needed, then N_{BAN1}=Min
(i,Non(k),Noff(k))；If N_{diff}> 0, i.e. output voltage changes, then N_{BAN1}=Min (i, Non (k), Noff (k)
N_{diff})；If N_{diff}< 0, i.e. output voltage changes, then N_{BAN1}=Min (i, Non (k)+N_{diff},Noff(k))。
B. according to N_{BAN1}And N_{diff}Control the switching of the bridge arm Neutron module.
Specifically, in N_{BAN1}When=Min (i, Non (k), Noff (k)), the minimum value why chosen in these three values is made
For N_{BAN1}, it is because of the case where state that will appear the submodule by certain investments or excision changes, then in bridge arm current i_{arm}
Direction be timing, need excision state submodule sorted lists in select the smallest N of voltage_{BAN1}A submodule investment, with
And the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}A submodule excision；
In N_{BAN1}=Min (i, Non (k), Noff (k)N_{diff}) when, in bridge arm current i_{arm}Direction 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 N_{BAN1}A submodule excision, while in order to meet the needs of output predeterminated voltage, it should be by additional N_{diff}A submodule
Investment, i.e. investment (N_{BAN1}+N_{diff}) a submodule, it is therefore desirable to selection voltage is minimum in excision state submodule sorted lists
(N_{BAN1}+N_{diff}) a submodule investment, and the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}Height
Module excision；
In N_{BAN1}=Min (i, Non (k)+N_{diff}, Noff (k)) when, in bridge arm current i_{arm}Direction be timing, need
The smallest N of voltage is selected in excision state submodule sorted lists_{BAN1}A submodule investment, and in investment state submodule row
Maximum (the N of voltage is selected in sequence table_{BAN1}N_{diff}) excision of a submodule.
The step S1047 includes the following steps C and D.
C. as bridge arm current i_{arm}Direction when being negative, according to find j value, N_{diff}, Non (k) and Noff (k) are obtained should
The corresponding second additional adjustment number of modules N of bridge arm_{BAN2}.Wherein, N_{diff}Alternatively 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: N_{diff}> 0, N_{diff}=0 and N_{diff}<0。
Specifically, if N_{diff}=0, the switching state for changing submodule because of voltage modulated is not needed, then N_{BAN2}=Min
(j,Non(k),Noff(k))；If N_{diff}> 0, i.e. output voltage changes, then N_{BAN2}=Min (j, Non (k), Noff (k)
N_{diff})；If N_{diff}< 0, i.e. output voltage changes, then N_{BAN2}=Min (j, Non (k)+N_{diff},Noff(k))。
D. according to N_{BAN2}And N_{diff}Control the switching of the bridge arm Neutron module.
Specifically, in N_{BAN2}When=Min (j, Non (k), Noff (k)), the minimum value why chosen in these three values is made
For N_{BAN2}, it is because of the case where state that will appear the submodule by certain investments or excision changes, then in bridge arm current i_{arm}
Direction when being negative, need to select the maximum N of voltage in excision state submodule sorted lists_{BAN2}A submodule investment, with
And the smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}A submodule excision；
In N_{BAN2}=Min (j, Non (k), Noff (k)N_{diff}) when, in bridge arm current i_{arm}Direction when being negative, need
Maximum (the N of voltage is selected in excision state submodule sorted lists_{BAN2}+N_{diff}) a submodule investment, and in investment state subgroup
The smallest N of voltage is selected in module sorted lists_{BAN2}A submodule excision；
In N_{BAN2}=Min (j, Non (k)+N_{diff}, Noff (k)) when, in bridge arm current i_{arm}Direction when being negative, need
The maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, and in investment state submodule row
The smallest (the N of voltage is selected in sequence table_{BAN2}N_{diff}) excision of a submodule.
In addition, in practical applications, if the capacitance voltage maximum value U of bridge arm Neutron module_{max}With capacitance voltage minimum value
U_{min}Difference be not more than h*U_{ave}(i.e. U_{max}U_{min}≤h*U_{ave}) when, voltagesharing is not present, does not need to press submodule
Modulation, only the capacitance voltage maximum value U of bridge arm Neutron module_{max}With capacitance voltage minimum value U_{min}Difference be greater than h*U_{ave}(i.e.
U_{max}U_{min}>h*U_{ave}) 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 period_{max}With capacitance voltage minimum value
U_{min}；Calculate the capacitance voltage maximum value U of each bridge arm Neutron module_{max}With capacitance voltage minimum value U_{min}Difference.
The step S104 further includes following steps: if the capacitance voltage maximum value U of bridge arm Neutron module_{max}With capacitor electricity
Press minimum value U_{min}Difference be greater than h*U_{ave}, 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 i_{arm}Directional information.
S202. the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period is obtained_{ave}, in each bridge arm
The capacitance voltage maximum value U of submodule_{max}With capacitance voltage minimum value U_{min}。
S203. the capacitance voltage maximum value U of each bridge arm Neutron module is calculated_{max}With capacitance voltage minimum value U_{min}Difference, if
U_{max}U_{min}>h*U_{ave}, 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 (k1) 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 calculated_{diff}=
Non(k)Non(k1)。
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 i_{arm}Direction, if bridge arm current i_{arm}Direction be positive (i.e. i_{arm}> 0) step, is then executed
Rapid S209；If bridge arm current i_{arm}Direction be negative (i.e. i_{arm}< 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 U_{1}To U_{m}, the capacitance voltage of the n submodule is U from big to small_{m+1}To U_{N}。
S210. first sorted lists are directed to, U is calculated_{i}U_{Ni+1}, i is incremented by since 1, and i is integer, and successively with
h*U_{ave}It is compared, meets U until finding_{i}U_{Ni+1}<h*U_{ave}I value.
S211. judge N_{diff}Value, if N_{diff}=0, then follow the steps S212；If N_{diff}> 0, then follow the steps S214；If
N_{diff}< 0, then follow the steps S216.
S212. N is enabled_{BAN1}=Min (i, Non (k), Noff (k)).
S213. the smallest N of voltage is selected in excision state submodule sorted lists_{BAN1}A submodule investment, Yi Ji
The maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}A submodule excision.
S214. N is enabled_{BAN1}=Min (i, Non (k), Noff (k)N_{diff})。
S215. the smallest (the N of voltage is selected in excision state submodule sorted lists_{BAN1}+N_{diff}) a submodule investment,
And the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}A submodule excision.
S216. N is enabled_{BAN1}=Min (i, Non (k)+N_{diff},Noff(k))。
S217. the smallest N of voltage is selected in excision state submodule sorted lists_{BAN1}A submodule investment, Yi Ji
Maximum (the N of voltage is selected in investment state submodule sorted lists_{BAN1}N_{diff}) 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 U_{1}To U_{n}, the capacitance voltage of the m submodule is U from big to small_{n+1}To U_{N}。
S219. second sorted lists are directed to, U is calculated_{j}U_{Nj+1}, j is incremented by since 1, and j is integer, and successively with
h*U_{ave}It is compared, meets U until finding_{j}U_{Nj+1}<h*U_{ave}J value.
S220. judge N_{diff}Value, if N_{diff}=0, then follow the steps S221；If N_{diff}> 0, then follow the steps S223；If
N_{diff}< 0, then follow the steps S225.
S221. N is enabled_{BAN2}=Min (j, Non (k), Noff (k)).
S222. the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, Yi Ji
The smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}A submodule excision.
S223. N is enabled_{BAN2}=Min (j, Non (k), Noff (k)N_{diff})。
S224. maximum (the N of voltage is selected in excision state submodule sorted lists_{BAN2}+N_{diff}) a submodule investment,
And the smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}A submodule excision.
S225. N is enabled_{BAN2}=Min (j, Non (k)+N_{diff},Noff(k))。
S226. the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, Yi Ji
The smallest (the N of voltage is selected in investment state submodule sorted lists_{BAN2}N_{diff}) 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 abovementioned 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 pregenerates 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 (k1) 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 abovedescribed 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 i_{arm}Directional information；
Acquiring unit 200 is used to obtain the capacitance present average voltage of each bridge arm Neutron module in this secondary control period
U_{ave}, 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 i_{arm}Direction 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 block_{ave}；And in bridge arm current i_{arm}Direction 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*U_{ave}。
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 (k1) 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 i_{arm}Direction 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 small_{1}To U_{m}, the capacitor of the n submodule
Voltage is U from big to small_{m+1}To U_{N}；
First searching module 402 calculates U for being directed to first sorted lists_{i}U_{Ni+1}, i is incremented by since 1, and i
For integer, and successively with h*U_{ave}It is compared, meets U until finding_{i}U_{Ni+1}<h*U_{ave}I value；
First switching module 403, the i value found for basis, Non (k) and Non (k1) control the bridge arm Neutron module
Switching；
Second comprising modules 404, in bridge arm current i_{arm}Direction 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 small_{1}To U_{n}, the capacitor of the m submodule
Voltage is U from big to small_{n+1}To U_{N}；
Second searching module 405 calculates U for being directed to second sorted lists_{j}U_{Nj+1}, j is incremented by since 1, and j
For integer, and successively with h*U_{ave}It is compared, meets U until finding_{j}U_{Nj+1}<h*U_{ave}J value；
Second switching module 406, the j value found for basis, Non (k) and Non (k1) 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 module_{diff}=Non (k)Non (k1).
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 i_{arm}Direction be timing according to the i found
Value, N_{diff}, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge arm_{BAN1}；And according to N_{BAN1}With
N_{diff}Control the switching of the bridge arm Neutron module.
And the first switching module 403 is specifically used for,
In N_{diff}When=0, make N_{BAN1}=Min (i, Non (k), Noff (k)), and in excision state submodule sorted lists
Select the smallest N of voltage_{BAN1}A submodule investment, and selection voltage is maximum in investment state submodule sorted lists
N_{BAN1}A submodule excision；
In N_{diff}When > 0, make N_{BAN1}=Min (i, Non (k), Noff (k)N_{diff}), and in excision state submodule Sorted list
The smallest (the N of voltage is selected in table_{BAN1}+N_{diff}) a submodule investment, and electricity is selected in investment state submodule sorted lists
Press maximum N_{BAN1}A submodule excision；
In N_{diff}When < 0, make N_{BAN1}=Min (i, Non (k)+N_{diff}, Noff (k)), and in excision state submodule Sorted list
The smallest N of voltage is selected in table_{BAN1}A submodule investment, and selection voltage is maximum in investment state submodule sorted lists
(N_{BAN1}N_{diff}) excision of a submodule.
Second switching module 406 of control unit is also used in bridge arm current i_{arm}Direction when being negative according to the j found
Value, N_{diff}, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge arm_{BAN2}；And according to N_{BAN2}With
N_{diff}Control the switching of the bridge arm Neutron module.
And the second switching module 406 is specifically used for,
In N_{diff}When=0, make N_{BAN2}=Min (j, Non (k), Noff (k)), and in N_{BAN2}=Min (j, Non (k), Noff
(k)) when, the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, and in investment shape
The smallest N of voltage is selected in state submodule sorted lists_{BAN2}A submodule excision；
In N_{diff}When > 0, make N_{BAN2}=Min (j, Non (k), Noff (k)N_{diff}), and in N_{BAN2}=Min (j, Non (k),
Noff(k)N_{diff}) when, the maximum (N of voltage is selected in excision state submodule sorted lists_{BAN2}+N_{diff}) a submodule throws
Enter, and selects the smallest N of voltage in investment state submodule sorted lists_{BAN2}A submodule excision；
In N_{diff}When < 0, make N_{BAN2}=Min (j, Non (k)+N_{diff}, Noff (k)), and in N_{BAN2}=Min (j, Non (k)+
N_{diff}, Noff (k)) when, the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, and
The smallest (the N of voltage is selected in investment state submodule sorted lists_{BAN2}N_{diff}) 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*U_{ave}When, 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 directcurrent 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 directcurrent 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 i_{arm}Directional information；
Obtain the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period_{ave}, 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 i_{arm}Direction 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*U_{ave}；If bridge arm current i_{arm}Direction 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 removed_{ave}。
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 (k1) of module, wherein k is the integer greater than 1；
As bridge arm current i_{arm}Direction 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
U_{1}To U_{m}, the capacitance voltage of the n submodule is U from big to small_{m+1}To U_{N}；
For first sorted lists, U is calculated_{i}U_{Ni+1}, i is incremented by since 1, and i is integer, and successively with h*U_{ave}It carries out
Compare, meets U until finding_{i}U_{Ni+1}<h*U_{ave}I value；
The switching of the bridge arm Neutron module is controlled according to the i value that finds, Non (k) and Non (k1)；
As bridge arm current i_{arm}Direction 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
U_{1}To U_{n}, the capacitance voltage of the m submodule is U from big to small_{n+1}To U_{N}；
For second sorted lists, U is calculated_{j}U_{Nj+1}, j is incremented by since 1, and j is integer, and successively with h*U_{ave}It carries out
Compare, meets U until finding_{j}U_{Nj+1}<h*U_{ave}J value；
The switching of the bridge arm Neutron module is controlled according to the j value that finds, Non (k) and Non (k1).
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 period_{diff}=Non (k)Non
(k1)；
Obtain the excision number Noff (k) of each bridge arm Neutron module in this secondary control period；
As bridge arm current i_{arm}Direction be timing, i value that the basis is found, Non (k) and Non (k1) are controlled in the bridge arm
The step of switching of submodule includes:
According to find i value, N_{diff}, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge arm_{BAN1}；
According to N_{BAN1}And N_{diff}Control the switching of the bridge arm Neutron module；
As bridge arm current i_{arm}Direction when being negative, j value that the basis is found, Non (k) and Non (k1) are controlled in the bridge arm
The step of switching of submodule includes:
According to find j value, N_{diff}, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge arm_{BAN2}；
According to N_{BAN2}And N_{diff}Control 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, N_{diff}, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules of the bridge arm
N_{BAN1}The step of include:
If N_{diff}=0, then N_{BAN1}=Min (i, Non (k), Noff (k))；If N_{diff}> 0, then N_{BAN1}=Min (i, Non (k), Noff
(k)N_{diff})；If N_{diff}< 0, then N_{BAN1}=Min (i, Non (k)+N_{diff},Noff(k))；
It is described according to N_{BAN1}And N_{diff}The step of controlling the switching of the bridge arm Neutron module include:
In N_{BAN1}When=Min (i, Non (k), Noff (k)), selection voltage is the smallest in excision state submodule sorted lists
N_{BAN1}A submodule investment, and the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}A submodule excision；
In N_{BAN1}=Min (i, Non (k), Noff (k)N_{diff}) when, voltage is selected most in excision state submodule sorted lists
Small (N_{BAN1}+N_{diff}) a submodule investment, and the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}It is a
Submodule excision；
In N_{BAN1}=Min (i, Non (k)+N_{diff}, Noff (k)) when, voltage is selected most in excision state submodule sorted lists
Small N_{BAN1}A submodule investment, and the maximum (N of voltage is selected in investment state submodule sorted lists_{BAN1}N_{diff}) a
Submodule excision；
J value that the basis is found, N_{diff}, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules of the bridge arm
N_{BAN2}The step of include:
If N_{diff}=0, then N_{BAN2}=Min (j, Non (k), Noff (k))；If N_{diff}> 0, then N_{BAN2}=Min (j, Non (k), Noff
(k)N_{diff})；If N_{diff}< 0, then N_{BAN2}=Min (j, Non (k)+N_{diff},Noff(k))；
It is described according to N_{BAN2}And N_{diff}The step of controlling the switching of the bridge arm Neutron module include:
In N_{BAN2}When=Min (j, Non (k), Noff (k)), selection voltage is maximum in excision state submodule sorted lists
N_{BAN2}A submodule investment, and the smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}A submodule excision；
In N_{BAN2}=Min (j, Non (k), Noff (k)N_{diff}) when, voltage is selected most in excision state submodule sorted lists
Big (N_{BAN2}+N_{diff}) a submodule investment, and the smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}It is a
Submodule excision；
In N_{BAN2}=Min (j, Non (k)+N_{diff}, Noff (k)) when, voltage is selected most in excision state submodule sorted lists
Big N_{BAN2}A submodule investment, and the smallest (N of voltage is selected in investment state submodule sorted lists_{BAN2}N_{diff}) 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*U_{ave}, 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 i_{arm}Directional information；
Acquiring unit, for obtaining the capacitance present average voltage U of each bridge arm Neutron module in this secondary control period_{ave}, 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 i_{arm}Direction 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*U_{ave}；And in bridge arm current i_{arm}Direction 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*U_{ave}。
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 (k1) 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 i_{arm}Direction 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 small_{1}To U_{m}, the capacitance voltage of the n submodule is from big
To small for U_{m+1}To U_{N}；
First searching module calculates U for being directed to first sorted lists_{i}U_{Ni+1}, i is incremented by since 1, and i is integer,
And successively with h*U_{ave}It is compared, meets U until finding_{i}U_{Ni+1}<h*U_{ave}I value；
First switching module, the i value found for basis, Non (k) control the switching of the bridge arm Neutron module with Non (k1)；
Second comprising modules, in bridge arm current i_{arm}Direction 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 small_{1}To U_{n}, the capacitance voltage of the m submodule is from big
To small for U_{n+1}To U_{N}；
Second searching module calculates U for being directed to second sorted lists_{j}U_{Nj+1}, j is incremented by since 1, and j is integer,
And successively with h*U_{ave}It is compared, meets U until finding_{j}U_{Nj+1}<h*U_{ave}J value；
Second switching module, the j value found for basis, Non (k) control the switching of the bridge arm Neutron module with Non (k1).
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 N_{diff}=Non (k)Non (k1)；
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 i_{arm}Direction be timing according to the i value found,
N_{diff}, Non (k) and Noff (k) obtain the corresponding first additional adjustment number of modules N of the bridge arm_{BAN1}；And according to N_{BAN1}And N_{diff}
Control the switching of the bridge arm Neutron module；
Second switching module of described control unit is also used to, in bridge arm current i_{arm}Direction when being negative according to the j value found,
N_{diff}, Non (k) and Noff (k) obtain the corresponding second additional adjustment number of modules N of the bridge arm_{BAN2}；And according to N_{BAN2}And N_{diff}
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 N_{diff}When=0, make N_{BAN1}=Min (i, Non (k), Noff (k)), and selected in excision state submodule sorted lists
The smallest N of voltage_{BAN1}A submodule investment, and the maximum N of voltage is selected in investment state submodule sorted lists_{BAN1}It is a
Submodule excision；
In N_{diff}When > 0, make N_{BAN1}=Min (i, Non (k), Noff (k)N_{diff}), and in excision state submodule sorted lists
Select the smallest (N of voltage_{BAN1}+N_{diff}) a submodule investment, and selection voltage is most in investment state submodule sorted lists
Big N_{BAN1}A submodule excision；
In N_{diff}When < 0, make N_{BAN1}=Min (i, Non (k)+N_{diff}, Noff (k)), and in excision state submodule sorted lists
Select the smallest N of voltage_{BAN1}A submodule investment, and selection voltage is maximum in investment state submodule sorted lists
(N_{BAN1}N_{diff}) excision of a submodule；
Second switching module is specifically used for,
In N_{diff}When=0, make N_{BAN2}=Min (j, Non (k), Noff (k)), and in N_{BAN2}=Min (j, Non (k), Noff (k))
When, the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, and in investment state subgroup
The smallest N of voltage is selected in module sorted lists_{BAN2}A submodule excision；
In N_{diff}When > 0, make N_{BAN2}=Min (j, Non (k), Noff (k)N_{diff}), and in N_{BAN2}=Min (j, Non (k), Noff
(k)N_{diff}) when, the maximum (N of voltage is selected in excision state submodule sorted lists_{BAN2}+N_{diff}) a submodule investment, with
And the smallest N of voltage is selected in investment state submodule sorted lists_{BAN2}A submodule excision；
In N_{diff}When < 0, make N_{BAN2}=Min (j, Non (k)+N_{diff}, Noff (k)), and in N_{BAN2}=Min (j, Non (k)+N_{diff},
Noff (k)) when, the maximum N of voltage is selected in excision state submodule sorted lists_{BAN2}A submodule investment, and throwing
Enter the selection the smallest (N of voltage in state submodule sorted lists_{BAN2}N_{diff}) excision of a submodule.
10. the equal pressure modulating device according to any one of claim 69, 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*U_{ave}When, control the switching of the bridge arm Neutron module；Otherwise, pressure processing is not made to the bridge arm.
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