CN205754045U - Auxiliary capacitor centralized half-bridge MMC self-balancing topology based on equality constraints - Google Patents

Abstract

This utility model provides the centralized half-bridge MMC of auxiliary capacitor based on equality constraint from all pressing topology.Half-bridge MMC is from all pressing topology, by half-bridge MMC model with from all pressure subsidiary loop joint mappings.Half-bridge MMC model and 6 in all pressure subsidiary loop is by subsidiary loopNIndividual mechanical switch generation electrical link, mechanical switch closes, and both constitute the centralized half-bridge MMC of auxiliary capacitor based on equality constraint and certainly all press topology, mechanical switch to open, and topoligical equivalence is half-bridge MMC topology.In the case of not emphasizing two kinds of topological variations, 6 in all pressure subsidiary loopsNIndividual mechanical switch can omit, and substitutes with wire, directly constitutes the centralized half-bridge MMC of auxiliary capacitor based on equality constraint from all pressing topology.This half-bridge MMC is from all pressing topology, do not rely on special Pressure and Control, it is possible on the basis of completing the conversion of orthogonal stream energy, spontaneously realize the equilibrium of submodule capacitor voltage, submodule can be reduced simultaneously accordingly and trigger frequency and capacitor's capacity, it is achieved the fundamental frequency modulation of half-bridge MMC.

Description

Auxiliary Capacitor Concentrated Half Bridge Based on Equality Constraints MMC self-balancing topology

technical field

The utility model relates to the field of flexible power transmission, in particular to an auxiliary capacitance centralized half-bridge MMC self-equalizing topology based on equality constraints.

Background technique

Modular multilevel converter (MMC) is the development direction of DC transmission technology in the future. MMC uses sub-module (SM) cascading to construct converter valves, which avoids the direct series connection of a large number of devices and reduces the impact on devices. Consistency requirements, while easy to expand and redundant configuration. As the number of levels increases, the output waveform is close to sinusoidal, which can effectively avoid the defects of low-level VSC-HVDC.

The half-bridge MMC is composed of half-bridge sub-modules. The half-bridge sub-module is composed of 2 IGBT modules, 1 sub-module capacitor, 1 thyristor and 1 mechanical switch, with low cost and low operating loss.

Unlike two-level and three-level VSCs, the DC side voltage of the half-bridge MMC is not supported by a large capacitor, but is supported by a series of independent suspension sub-module capacitors in series. In order to ensure the waveform quality of the voltage output on the AC side and to ensure that each power semiconductor device in the module bears the same stress, and to better support the DC voltage and reduce interphase circulation, it is necessary to ensure the periodic flow of the sub-module capacitor voltage in the bridge arm power is in a dynamically stable state.

The sorting voltage equalization algorithm based on capacitor voltage sorting is currently the mainstream idea to solve the capacitor voltage equalization problem of the half-bridge sub-modules in the half-bridge MMC. exposed some of its inherent flaws. First of all, the realization of the sorting function must rely on the millisecond-level sampling of the capacitor voltage, which requires the cooperation of a large number of sensors and fiber optic channels; secondly, when the number of half-bridge sub-modules increases, the calculation amount of the capacitor voltage sorting increases rapidly. Hardware design brings huge challenges; in addition, the implementation of the sorting voltage equalization algorithm has high requirements on the switching frequency of sub-modules, which are closely related to the voltage leveling effect. In practice, it may be due to the limitation of the voltage leveling effect , the trigger frequency of the sub-module has to be increased, which in turn increases the loss of the converter.

Literature "A DC-Link Voltage Self-Balance Method for a Diode-Clamped Modular Multilevel Converter With "Minimum Number of Voltage Sensors", put forward an idea of relying on clamping diodes and transformers to realize the voltage balance of MMC sub-module capacitors. However, the design of this scheme destroys the modular characteristics of sub-modules to a certain extent, and the energy exchange of sub-module capacitors The channel is also limited to the phase, and the existing structure of the MMC cannot be fully utilized. The introduction of three transformers will not only complicate the control strategy, but also bring a large transformation cost.

Utility model content

In view of the above problems, the purpose of this utility model is to propose an economical, modular, half-bridge MMC self-balancing topology that does not depend on the voltage-balancing algorithm, and can correspondingly reduce the trigger frequency and capacitance of the sub-modules.

Concrete constitutional mode of the present utility model is as follows.

Auxiliary capacitor centralized half-bridge MMC self-balancing topology based on equality constraints, including a half-bridge MMC model composed of three phases A, B, and C. The three phases A, B, and C are respectively composed of 2 N half-bridge sub-modules. Two bridge arm reactors are connected in series; including a self-balanced auxiliary circuit composed of 6 N mechanical switches, 6 N + 5 clamping diodes, 2 auxiliary capacitors, and 2 auxiliary IGBT modules.

The above-mentioned auxiliary capacitor centralized half-bridge MMC self-balancing topology based on equality constraints, the first sub-module of the upper bridge arm of phase A, the negative pole of the sub-module capacitor is downward and the second sub-module IGBT module of the upper bridge arm of phase A The middle point of the sub-module IGBT module is connected upwards with the positive pole of the DC bus; the i -th sub-module of the upper bridge arm of phase A, where the value of i is 2 to N -1, the negative pole of the sub-module capacitor is downwards with the positive pole of the DC bus. The midpoint of the i +1 sub-module IGBT module of the upper bridge arm of phase A is connected, and the midpoint of the IGBT module of the sub-module is upwardly connected with the negative electrode of the i -1 submodule capacitor of the upper bridge arm of phase A; the upper bridge arm of phase A The Nth sub-module of the sub-module, the negative pole of the sub-module capacitor is connected downwards to the midpoint of the first sub-module IGBT module of the lower bridge arm of the A phase through two bridge arm reactors, and the midpoint of the IGBT module of the sub-module is upwardly connected to the upper side of the A phase The N -1th sub-module of the bridge arm is connected to the negative pole of the capacitor; the i -th sub-module of the lower bridge arm of the A phase, where the value of i is 2 to N -1, the negative pole of the sub-module capacitor of the lower bridge arm of the A phase is downward The i +1th sub-module IGBT module midpoint of the IGBT module is connected upward, and the IGBT module midpoint is upwardly connected to the negative electrode of the i -1th submodule capacitor of the lower bridge arm of the A phase; the Nth submodule of the lower bridge arm of the A phase, its The negative pole of the sub-module capacitor is connected downward to the negative pole of the DC bus, and the midpoint of the sub-module IGBT module is connected upward to the negative pole of the capacitor of the N -1th sub-module of the lower bridge arm of the A phase; the first sub-module of the upper bridge arm of the B-phase, The positive pole of the sub-module capacitor is connected upwards to the positive pole of the DC bus, and the midpoint of the sub-module IGBT module is connected downward to the positive pole of the second sub-module capacitor of the upper bridge arm of the B phase; the i -th sub-module of the upper bridge arm of the B phase, where The value of i is 2 to N -1, the positive pole of the sub-module capacitor is connected upward to the midpoint of the I -1th sub-module IGBT module of the upper bridge arm of phase B, and the midpoint of the sub-module IGBT module is downwardly connected to the upper pole of the B-phase The i +1th sub-module capacitor of the bridge arm is connected to the positive pole; the Nth sub-module of the upper bridge arm of the B phase is connected to the positive pole of the sub-module capacitor of the N -1th sub-module IGBT module of the upper bridge arm of the B-phase upward. , the midpoint of the IGBT module of its sub-module is downwardly connected to the positive electrode of the first sub-module capacitor of the lower bridge arm of the B phase through two bridge arm reactors; the i -th sub-module of the lower bridge arm of the B phase, where the value of i is 2～ N -1, the positive electrode of the sub-module capacitor is connected upward to the midpoint of the I-1th sub-module IGBT module of the lower bridge arm of the B phase, and the midpoint of the IGBT module of the sub-module is downwardly connected to the i - th sub-module of the lower bridge arm of the B phase The +1 sub-module capacitor is connected to the positive pole; the N -th sub-module of the lower bridge arm of the B phase, the positive pole of the sub-module capacitor is connected upward to the midpoint of the IGBT module of the N -1 sub-module of the lower bridge arm of the B phase, and the sub-module IGBT module The midpoint is downwardly connected to the negative pole of the DC bus; the connection mode of the upper and lower bridge arm sub-modules of the C phase is consistent with that of the A phase or B phase.

The above-mentioned auxiliary capacitor centralized half-bridge MMC self-balancing topology based on equality constraints, in the self-balancing auxiliary circuit, the positive pole of the first auxiliary capacitor is connected to the negative pole of the auxiliary IGBT module, connected to the clamping diode and merged into the positive pole of the DC bus; the second auxiliary capacitor The negative pole of the capacitor is connected to the positive pole of the auxiliary IGBT module, which is connected to the clamping diode and merged into the negative pole of the DC bus. Clamping diode, connect the capacitor of the first sub -module in the upper bridge arm of phase A to the anode of the first auxiliary capacitor through a mechanical switch; Positive pole, where the value of i is 1 to N -1; connect the Nth sub-module capacitor in the upper bridge arm of phase A to the positive pole of the first sub-module capacitor in the lower bridge arm of phase A through a mechanical switch; connect the lower bridge of phase A through a mechanical switch The i -th sub-module capacitor in the arm is connected to the positive electrode of the i +1 sub-module capacitor in the lower bridge arm of phase A, where the value of i is 1 to N -1; the capacitor of the N -th sub-module in the lower bridge arm of phase A is connected to The positive terminal of the second auxiliary capacitor. Clamp diode, connect the capacitor of the first sub-module in the upper bridge arm of phase B to the cathode of the first auxiliary capacitor through a mechanical switch; connect the capacitor of the i -th sub-module in the upper bridge arm of phase B to the capacitor of the i +1 sub-module Negative pole, where the value of i is 1 to N -1; connect the Nth sub-module capacitor in the upper bridge arm of phase B to the negative pole of the first sub-module capacitor in the lower bridge arm of phase B through a mechanical switch; connect the lower bridge of phase B through a mechanical switch The i -th sub-module capacitor in the arm is connected to the negative electrode of the i +1 sub-module capacitor in the lower bridge arm of phase B, where the value of i is 1 to N -1; the capacitor of the N -th sub-module in the lower bridge arm of phase B is connected to the capacitor through a mechanical switch. The negative terminal of the second auxiliary capacitor. The connection relationship of the C-phase clamping diode corresponds to the connection relationship of its sub-modules.

Description of drawings

Fig. 1 is a structural schematic diagram of a half-bridge sub-module;

Figure 2 is the self-balancing topology of the auxiliary capacitor centralized half-bridge MMC based on equality constraints.

detailed description

In order to further illustrate the performance and working principle of the utility model, the structure and working principle of the utility model will be described in detail below in conjunction with the accompanying drawings. However, the self-equalizing topology of the half-bridge MMC based on this principle is not limited to FIG. 2 .

Referring to Figure 2, the self-balancing topology of the half-bridge MMC with centralized auxiliary capacitors based on equality constraints includes a half-bridge MMC model composed of three phases A, B, and C. Each bridge arm of the three phases A, B, and C is respectively composed of N half-bridge sub-modules and 1 bridge arm reactor are connected in series; including 6 N mechanical switches, 6 N + 5 clamping diodes, 2 auxiliary capacitors, and 2 auxiliary IGBT modules. circuit.

In the half-bridge MMC model, the first sub-module of the upper bridge arm of phase A, its sub-module capacitor C _{au_1} negative pole is connected downward to the midpoint of the second sub-module IGBT module of the upper bridge arm of phase A, and the sub-module IGBT module The point is connected upward to the positive pole of the DC bus; the i -th sub-module of the upper bridge arm of phase A, where the value of i is 2 to N -1, and the negative pole of the sub-module capacitor C _{au_ i} is downwardly connected to the i-th sub-module of the upper bridge arm of phase A i +1 sub-modules are connected to the midpoint of the IGBT module, and the midpoint of the submodule IGBT module is upwardly connected to the cathode of the i -1th submodule capacitor C _{au_ i -1} of the upper bridge arm of the A phase; N sub-modules, the negative pole of the sub-module capacitor C _{au_ N} is connected to the middle point of the first sub-module IGBT module of the lower bridge arm of phase A through two bridge arm reactors L 0 downward, _and the mid-point of the sub-module IGBT module is connected upward to Capacitance C of the N -1th sub-module of the upper bridge arm of phase A _{­ au_ N -1 is connected to the negative pole} ; the i- th sub -module of the lower bridge arm of the A phase, where the value of i is 2 to N -1 , the sub-module capacitance C _{al_ i negative pole} is downward and the i -th sub-module of the lower bridge arm of the A phase The midpoint of the +1 sub-module IGBT module is connected, and the midpoint of the IGBT module is upwardly connected to the cathode of the i -1th sub-module capacitor C _{al_ i -1} of the lower bridge arm of the A phase; the Nth sub -module of the lower bridge arm of the A phase , the negative pole of the sub-module capacitor C _{al_ N} is connected downward to the negative pole of the DC bus, and the midpoint of the sub-module IGBT module is upwardly connected to the negative pole of the N -1th sub-module capacitor C _{al_ N- 1} of the lower bridge arm of phase A; B In the first sub-module of the upper bridge arm of the phase, the positive pole of the sub-module capacitor C _{bu_1} is connected upward to the positive pole of the DC bus, and the midpoint of the sub-module IGBT module is downwardly connected to the positive pole of the second sub-module capacitor C _{bu_2} of the upper bridge arm of the B phase Connection; The i -th sub-module of the upper bridge arm of the B-phase, where the value of i is 2 to N -1, the positive pole of the sub-module capacitor C _{bu_ i} is upward and the i - 1th sub-module IGBT module of the upper bridge arm of the B-phase The middle point of the sub-module IGBT module is connected downward to the positive electrode of the i +1 sub-module capacitor C _{bu_ i +1} of the upper bridge arm of the B phase; the Nth sub -module of the upper bridge arm of the B phase, its sub-module Capacitance C _{­ The positive pole of bu_ N} is connected upward to the middle point of the IGBT module of the N - 1th sub-module of the upper bridge arm of the B phase, and the midpoint of the IGBT module of the sub-module is downwardly passed through two bridge arm reactors L 0 _and connected to the first sub-module IGBT module of the lower bridge arm of the B phase One sub-module capacitor C _{bl_1} is connected to the positive pole; the i -th sub-module of the lower bridge arm of the B phase, where the value of i is 2 to N -1, the positive pole of the sub-module capacitor C _{bl_ i} is connected to the i-th sub-module of the lower bridge arm of the B phase The midpoint of i -1 sub-module IGBT module is connected, and the midpoint of the sub-module IGBT module is connected downward to the positive pole of the i+1 submodule capacitor C _{bl_ i +1} of the lower bridge arm of phase B; In the Nth sub-module, the positive pole of the sub-module capacitor Cbl_N is connected upward to the midpoint of the IGBT module of the N - _{1th submodule} of the lower bridge arm of the B phase, and the midpoint of the IGBT module of the submodule is downwardly connected to the negative pole of the DC bus. The connection mode of the sub-modules of the upper and lower bridge arms of phase C is the same as that of phase A.

In the self-balanced auxiliary circuit, the positive pole of the auxiliary capacitor C ₁ is connected to the auxiliary IGBT module T ₁ , the negative pole is connected to the clamping diode and merged into the positive pole of the DC bus; the negative pole of the auxiliary capacitor C ₂ is connected to the auxiliary IGBT module T ₂ , and the positive pole is connected to the clamping diode and merged into the DC bus. Bus negative pole. The clamping diode is connected to the positive pole of the first sub-module capacitor C _{au_1} in the upper bridge arm of phase A and the auxiliary capacitor C ₁ through the mechanical switch K _{au_13} ; it is connected to the upper pole of the A phase through the mechanical switch K _{au_ i 3} and K _{au_ ( i +1 ) 3} The i -th sub-module capacitor C _{au_ i in the bridge arm and} the i +1 -th sub-module capacitor C _{au_ i +1 are positive} , where the value of i is 1 to N -1 ; _connect A through mechanical switches K au_ _{N 3 and} K al_13 The capacitor C _{au_ N} of the Nth sub-module in the upper bridge arm of the phase and the _{positive electrode of the capacitor C al_1} of the first sub-module of the lower bridge arm of the A phase; _connect the lower bridge arm of the A phase through the mechanical switch K _{al_ i 3 ,} K _{al_ ( i +1 ) 3} The capacitor C _{al_ i} of the i -th sub-module and the _{positive electrode of the capacitor C al_ i +1} of the i +1 sub-module of the lower bridge arm of phase A, where the value of i is 1 to N -1 ; connect A through the mechanical switch K al_ _{N 3} The Nth sub-module capacitor C _{al_ N} in the lower bridge arm and the positive pole of the auxiliary capacitor C ₂ . The clamping diode is connected to the negative electrode of the first sub-module capacitor C _{bu_1} in the upper bridge arm of phase B and the auxiliary capacitor C ₁ through the mechanical switch K _{bu_13} ; it is connected to the upper pole of the B phase through the mechanical switch K _{bu_ i 3} and K _{bu_ ( i +1 ) 3} The capacitor C _{bu_ i of} the i -th sub-module in the bridge arm and the _{negative electrode of the capacitor C bu_ i +1} of the i +1 -th sub-module, where the value of i is 1 to N -1 ; _connect B through mechanical switches K bu_ _{N 3 and} K bl_13 The capacitor C _{bu_ N} of the Nth sub-module in the upper bridge arm of the phase and the _{negative electrode of the capacitor C bl_1} of the first sub-module of the lower bridge arm of the B-phase; _connect the lower bridge arm of the B-phase through the mechanical switch K _{bl_ i 3 ,} K _{bl_ ( i +1 ) 3} In the ith sub-module capacitance C _{­ bl_ i and} the i +1 sub-module capacitor C _{bl_ i +1 negative pole} of the lower bridge arm of the B phase, where the value of i is 1 to N -1 ; the Nth sub-module in the lower bridge arm of the B phase is connected through the mechanical switch K bl_ _{N 3} A sub-module capacitor C _{bl_ N and} auxiliary capacitor C 2 _negative . The connection relationship of the C-phase clamping diode is consistent with that of the A-phase.

6 N mechanical switches K _{au_ i 3} , K _{al_ i 3 ,} K bu_ i 3 , K _{bl_ i 3} , K _{cu_ i 3} , K _{cl_ i 3} are normally closed in the self-voltage equalizing auxiliary circuit, where the value of i is 1 ~ N . When the first sub-module capacitor C _{au_1} of the upper bridge arm of phase A is bypassed , the auxiliary IGBT module T ₁ is disconnected at this time, and the sub-module capacitor C _{au_1} and auxiliary capacitor C ₁ are connected in parallel through the clamp diode; Sub-module capacitance C _{­ When au_ i is bypassed} , where the value of i is 2 to N , the sub-module capacitor C _{au_ i and the sub-} module capacitor C au_ _{i- 1 are connected in parallel through the} clamp diode; the first sub-module capacitor C _{al_1} of the lower bridge arm of phase A When _{bypassing ,} the sub-module capacitor C _{al_1} is connected in parallel with the sub -module capacitor C _{au_ N} through the clamping diode and two bridge arm reactors L ₀ ; The value of 2～ N , the sub-module capacitance C _{al_ i and the} sub-module capacitance C _{al_ i -1 are connected in parallel through the} clamping diode; when the auxiliary IGBT module T 2 _{is closed} , the auxiliary capacitor C 2 is connected with the sub-module capacitance C _{through the} clamping diode _{al_ N} in parallel.

6 N mechanical switches K _{au_ i 3} , K _{al_ i 3 ,} K bu_ i 3 , K _{bl_ i 3} , K _{cu_ i 3} , K _{cl_ i 3} are normally closed in the self-voltage equalizing auxiliary circuit, where the value of i is 1 ~ N . When the auxiliary IGBT module T ₁ is closed, the auxiliary capacitor C ₁ and the sub-module capacitor C _{bu_1} are connected in parallel through the clamp diode; when the i -th sub-module capacitor C _{bu_ i of the upper bridge arm of the B phase is bypassed} , the value of i is 1 to N -1, the sub-module capacitor C _{bu_ i is connected in parallel with the} sub-module capacitor C _{bu_ i +1 through the} clamping diode; when the Nth sub -module capacitor C bu_ _{N of the upper bridge arm of phase B is bypassed} , the sub-module capacitor C bu_ _{N is} clamped Diode, two bridge arm reactors L ₀ and sub-module capacitor C _{bl_1} are connected in parallel; when the i -th sub-module capacitor C _{bl_ i} of the lower bridge arm of phase B is bypassed, the value of i is 1 to N -1, and the sub-module capacitor C _{bl_ i and} sub-module capacitor C _{bl_ i +1 are connected in parallel through a} clamping diode; when N sub -module capacitors C _{bl_ N of the lower bridge arm of phase B are bypassed} , the sub-module capacitor C _{bl_ N and auxiliary} capacitor C 2 are connected in parallel _{through a} clamping diode .

The trigger signal of the above auxiliary IGBT module T1 is consistent with the "logic sum" of the trigger signals of the _first submodule of the upper bridge arm of the A and C phases _; the trigger signal of the auxiliary IGBT module T2 is consistent with that of the Nth submodule of the lower bridge arm of the B phase The trigger signals are consistent. In the process of DC-AC energy conversion, each sub-module is switched on and bypassed alternately, and the auxiliary IGBT modules T ₁ and T ₂ are switched on and off alternately. Satisfy the following constraints:

It can be seen that the half-bridge MMC satisfies the following constraints in the dynamic process of completing DC-AC energy conversion:

The constraint conditions between C and B phases are consistent with those between A and B phases.

It can be seen from the above detailed description that the half-bridge MMC topology has the capability of sub-module capacitor voltage self-balancing.

Finally, it should be noted that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

Claims (6)

1. the centralized half-bridge MMC of auxiliary capacitor based on equality constraint is from all pressing topology, it is characterised in that: including the half-bridge MMC model being made up of A, B, C three-phase, A, B, C three-phase is respectively by 2NIndividual half-bridge submodule, 2 brachium pontis reactors are in series；Including by 6NIndividual mechanical switch, 6N+ 5 clamp diodes, 2 auxiliary capacitorsC ₁、C ₂, 2 auxiliary IGBT moduleT ₁、T ₂Constitute the most all presses subsidiary loop.

2. according to the centralized half-bridge MMC of auxiliary capacitor based on equality constraint described in right 1 from all pressing topology, it is characterised in that: the 1st submodule of brachium pontis, its submodule electric capacity in A phaseC _{­au­_1}Negative pole is connected with the 2nd of brachium pontis module I GBT module midpoint in A phase downwards, and its submodule IGBT module midpoint is upwards connected with dc bus positive pole；In A phase the of brachium pontisiIndividual submodule, whereiniValue be 2～N-1, its submodule electric capacityC­ _{au­_i} Negative pole is downwards with in A phase the of brachium pontisi+ 1 sub-module I GBT module midpoint is connected, and its submodule IGBT module midpoint is upwards with in A phase the of brachium pontisi-1 sub-module capacitanceC­_{au­_i-1}Negative pole is connected；In A phase the of brachium pontisNIndividual submodule, its submodule electric capacityC _{­au­_N}Negative pole is down through two brachium pontis reactorsL ₀1st sub-module I GBT module midpoint of brachium pontis lower with A phase is connected, and its submodule IGBT module midpoint is upwards with in A phase the of brachium pontisN-1 sub-module capacitanceC _{­ au­_N-1}Negative pole is connected；The of the lower brachium pontis of A phaseiIndividual submodule, whereiniValue be 2～N-1, its submodule electric capacityC­_{al­_i} Negative pole downwards with the of A phase time brachium pontisi+ 1 sub-module I GBT module midpoint is connected, the of its IGBT module midpoint upwards brachium pontis lower with A phasei-1 sub-module capacitanceC _{­al­_i-1}Negative pole is connected；The of the lower brachium pontis of A phaseNIndividual submodule, its submodule electric capacityC _{­al_N} Negative pole is connected with dc bus negative pole downwards, the of its submodule IGBT module midpoint upwards brachium pontis lower with A phaseN-1 sub-module capacitanceC _{­al­_N-1}Negative pole is connected；1st submodule of brachium pontis, its submodule electric capacity in B phaseC­ _{bu­_1}Positive pole is upwards connected with dc bus positive pole, its submodule IGBT module midpoint downwards with the 2nd sub-module capacitance of brachium pontis in B phaseC­_{bu­_2}Positive pole is connected；In B phase the of brachium pontisiIndividual submodule, whereiniValue be 2～N-1, its submodule electric capacityC­_{bu­_i} Positive pole is upwards with in B phase the of brachium pontisi-1 sub-module I GBT module midpoint is connected, and its submodule IGBT module midpoint is downwards with in B phase the of brachium pontisi+ 1 sub-module capacitanceC­ _{bu­_i+1}Positive pole is connected；In B phase the of brachium pontisNIndividual submodule, its submodule electric capacityC _{­ bu­_N} Positive pole is upwards with in B phase the of brachium pontisN-1 sub-module I GBT module midpoint is connected, and its submodule IGBT module midpoint is down through two brachium pontis reactorsL ₀1st sub-module capacitance of brachium pontis lower with B phaseC _{­bl­_1}Positive pole is connected；The of the lower brachium pontis of B phaseiIndividual submodule, whereiniValue be 2～N-1, its submodule electric capacityC­ _{bl_i} The of positive pole upwards brachium pontis lower with B phasei-1 sub-module I GBT module midpoint is connected, its submodule IGBT module midpoint downwards with the of B phase time brachium pontisi+ 1 sub-module capacitanceC­ _{bl­_i+1}Positive pole is connected；The of the lower brachium pontis of B phaseNIndividual submodule, its submodule electric capacityC­_{bl_N} Positive pole upwards brachium pontis lower with B phase theN-1 sub-module I GBT module midpoint is connected, and its submodule IGBT module midpoint is connected with dc bus negative pole downwards；The connected mode of C phase upper and lower bridge arm submodule can be consistent with A, it is also possible to consistent with B；At A, B, C phase upper and lower bridge armiMechanical switch it is parallel with respectively between the output lead up and down of individual submoduleK _{au_i1}、K _{al_i1}、K _{bu_i1}、K _{bl_i1}、K _{cu_i1}、K _{cl_i1}, and IGCTK _{au_i2}、K _{al_i2}、K _{bu_i2}、K _{bl_i2}、K _{cu_i2}、K _{cl_i2}, whereiniValue be 1～N；A, B, C three-phase status that above-mentioned annexation is constituted is consistent, and other topologys after three-phase symmetrized in turn are in interest field.

3. according to the centralized half-bridge MMC of auxiliary capacitor based on equality constraint described in right 1 from all pressing topology, it is characterised in that: in all pressure subsidiary loops, auxiliary capacitorC ₁Positive pole connects auxiliary IGBT moduleT ₁, negative pole connects clamp diode and is incorporated to dc bus positive pole；Auxiliary capacitorC ₂Negative pole connects auxiliary IGBT moduleT ₂, positive pole connects clamp diode and is incorporated to dc bus negative pole；Clamp diode, passes through mechanical switchK _{au_13}1st sub-module capacitance in brachium pontis in connection A phaseC­ _{au­_1}With auxiliary capacitorC ₁Positive pole；Pass through mechanical switchK _{au_i3}、K _{au_ (i+1 ) 3}Connect in A phase in brachium pontis theiIndividual sub-module capacitanceC­_{au­_i} Withi+ 1 sub-module capacitanceC­_{au­_i+1}Positive pole, whereiniValue be 1～N-1；Pass through mechanical switchK _{au_N3}、K _{al_13}Connect in A phase in brachium pontis theNIndividual sub-module capacitanceC _{­au­_N} Brachium pontis 1st sub-module capacitance lower with A phaseC­_{al­_1}Positive pole；Pass through mechanical switchK _{al_i3}、K _{al_ (i+1 ) 3}Connect in the lower brachium pontis of A phase theiIndividual sub-module capacitanceC _{­al­_i} Brachium pontis lower with A phase thei+ 1 sub-module capacitanceC _{­al­_i+1}Positive pole, whereiniValue be 1～N-1；Pass through mechanical switchK _{al_N3}Connect in the lower brachium pontis of A phase theNIndividual sub-module capacitanceC­_{al_N} With auxiliary capacitorC ₂Positive pole；Clamp diode, passes through mechanical switchK _{bu_13}1st sub-module capacitance in brachium pontis in connection B phaseC _{­bu­_1}With auxiliary capacitorC ₁Negative pole；Pass through mechanical switchK _{bu_i3}、K _{bu_ (i+1 ) 3}Connect in B phase in brachium pontis theiIndividual sub-module capacitanceC­_{bu­_i} Withi+ 1 sub-module capacitanceC _{­bu­_i+1}Negative pole, whereiniValue be 1～N-1；Pass through mechanical switchK _{bu_N3}、K _{bl_13}Connect in B phase in brachium pontis theNIndividual sub-module capacitanceC _{­bu­_N} Brachium pontis 1st sub-module capacitance lower with B phaseC _{­bl­_1}Negative pole；Pass through mechanical switchK _{bl_i3}、K _{bl_ (i+1 ) 3}Connect in the lower brachium pontis of B phase theiIndividual sub-module capacitanceC _{­ bl­_i} Brachium pontis lower with B phase thei+ 1 sub-module capacitanceC _{­bl­_i+1}Negative pole, whereiniValue be 1～N-1；Pass through mechanical switchK _{bl_N3}Connect in the lower brachium pontis of B phase theNIndividual sub-module capacitanceC­_{bl­_N} With auxiliary capacitorC ₂Negative pole；The annexation of C phase clamp diode is corresponding with the annexation of its submodule；In above-mentioned A, B, C three-phase 6NIndividual mechanical switchK _{au_i3}、K _{al_i3}、K _{bu_i3}、K _{bl_i3}、K _{cu_i3}、K _{cl_i3}, whereiniValue be 1～N, 6N+ 5 clamp diodes, 2 auxiliary capacitorsC ₁、C ₂, and 2 auxiliary IGBT moduleT ₁、T ₂, collectively form from all pressing subsidiary loop.

4. according to the centralized half-bridge MMC of auxiliary capacitor based on equality constraint described in right 1 from the most all pressing topology, it is characterised in that: in the most all pressure subsidiary loops 6NIndividual mechanical switchK _{au_i3}、K _{al_i3}、K _{bu_i3}、K _{bl_i3}、K _{cu_i3}、K _{cl_i3}Normally closed, whereiniValue be 1～N, first sub-module capacitance of brachium pontis in A phaseC­_{au­_1}During bypass, now assist IGBT moduleT ₁Disconnect, submodule electric capacityC­ _{au­_1}With auxiliary capacitorC ₁In parallel by clamp diode；Brachium pontis in A phaseiIndividual sub-module capacitanceC­_{au­_i} During bypass, whereiniValue be 2～N, submodule electric capacityC­_{au­_i} With submodule electric capacityC­_{au­_i-1}In parallel by clamp diode；Lower first the sub-module capacitance of brachium pontis of A phaseC _{­al_1}During bypass, submodule electric capacityC­_{al­_1}By clamp diode, two brachium pontis reactorsL ₀With submodule electric capacityC­ _{au­_N} In parallel；The lower brachium pontis of A phase theiIndividual sub-module capacitanceC _{­al_i} During bypass, whereiniValue be 2～N, submodule electric capacityC­_{al­_i} With submodule electric capacityC­_{al_i-1}In parallel by clamp diode；Auxiliary IGBT moduleT ₂During Guan Bi, auxiliary capacitorC ₂By clamp diode and submodule electric capacityC _{­al_N} In parallel；Auxiliary IGBT moduleT ₁During Guan Bi, auxiliary capacitorC ₁With submodule electric capacityC­_{bu­_1}In parallel by clamp diode；Brachium pontis in B phaseiIndividual sub-module capacitanceC­_{bu­_i} During bypass, whereiniValue be 1～N-1, submodule electric capacityC­_{bu­_i} With submodule electric capacityC­_{bu­_i+1}In parallel by clamp diode；Brachium pontis in B phaseNIndividual sub-module capacitanceC­_{bu_N} During bypass, submodule electric capacityC­ _{bu­_N} By clamp diode, two brachium pontis reactorsL ₀With submodule electric capacityC­ _{bl­_1}In parallel；The lower brachium pontis of B phase theiIndividual sub-module capacitanceC­_{bl_i} During bypass, whereiniValue be 1～N-1, submodule electric capacityC­_{bl­_i} With submodule electric capacityC­ _{bl_i+1}In parallel by clamp diode；The lower brachium pontis of B phaseNIndividual sub-module capacitanceC­_{bl_N} During bypass, submodule electric capacityC _{­bl­_N} With auxiliary capacitorC­ ₂In parallel by clamp diode；Wherein assist IGBT moduleT ₁" logic and " that trigger first submodule triggering signal of signal and brachium pontis in A, C phase consistent；Auxiliary IGBT moduleT ₂The lower brachium pontis of triggering signal and B phase theNThe triggering signal of individual submodule is consistent；During orthogonal stream energy is changed, each submodule alternately puts into, bypass, assists IGBT moduleT ₁、T ₂Being alternately closed, turn off, A phase upper and lower bridge arm submodule capacitor voltage, under the effect of clamp diode, meets lower column constraint,U _{C 1}≥U _{C ­au_1}≥U _{C ­au_2}…≥U _{C ­au_N} ≥U _{C ­al_1}≥U _{C ­al_2}…≥U _{C ­al_N} ≥U _{C 2}；B phase upper and lower bridge arm submodule capacitor voltage, under the effect of clamp diode, meets lower column constraint,U _{C 1}≤U _{C ­bu_1}≤U _{C ­bu_2}…≤U _{C ­bu_N} ≤U _{C ­bl_1}≤U _{C ­bl_2}…≤U _{C ­bl_N} ≤U _{C 2}；The centralized half-bridge MMC of auxiliary capacitor based on equality constraint is from all pressing topology, in dynamic process, and auxiliary capacitorC ₁Both can be as the highest electric capacity of A phase voltage, again can be as the minimum electric capacity of B phase voltage；Auxiliary capacitorC ₂Both can be as the minimum electric capacity of A phase voltage, again can be as the highest electric capacity of B phase voltage；Against two equality constraints, max(U _{C a­})=min(U _{C b}), min(U _{C a})=max(U _{C b}), in A, B phase upper and lower bridge arm 4NIndividual sub-module capacitance,C _{au_i} 、C_{al_i} 、C _{bu_i} 、C _{bl_i} , whereiniValue be 1～N, and auxiliary capacitorC ₁、C ₂, voltage be in self-balancing state, A, B are alternate possesses submodule capacitor voltage from the ability of equalization for topology；If the form of the composition of C phase is consistent with A in topology, then the constraints of C, B capacitive coupling voltage is consistent with capacitance voltage constraints between A, B；If the form of the composition of C phase is consistent with B in topology, then the constraints of A, C capacitive coupling voltage is consistent with capacitance voltage constraints between A, B, and topology possesses submodule capacitor voltage from the ability of equalization；In utilizing clamp diode to realize mutually between adjacent submodule on the basis of capacitive energy single-phase flow, rely on equality constraint max(between auxiliary capacitor voltageU _{C a­})=min(U _{C b}), min(U _{C a})=max(U _{C b}), or max(U _{C a­})=min(U _{C c}), min(U _{C a})=max(U _{C c}), or max(U _{C c})=min(U _{C b}), min(U _{C c})=max(U _{C b}), it is achieved the alternate flowing of capacitive energy constitutes the peripheral passage of capacitive energy, and then keeps alternate submodule capacitor voltage stable, is the protection content of this right.

5. according to the centralized half-bridge MMC of auxiliary capacitor based on equality constraint described in right 1 from all pressing topology, it is characterised in that: auxiliary capacitorC ₁、C ₂Both as the passage of A, B capacitive coupling energy exchange, again as the passage of B, C capacitive coupling energy exchange；The function of auxiliary capacitor focus utilization in topology the most all presses the device consumption in subsidiary loop to reduce；Auxiliary capacitorC ₁Function concentrate, auxiliary capacitorC ₂Function do not concentrate；Auxiliary capacitorC ₁Function do not concentrate, auxiliary capacitorC ₂Function concentrate topology in interest field.

6. according to the centralized half-bridge MMC of auxiliary capacitor based on equality constraint described in right 1 from all pressing topology, it is characterized in that: the centralized half-bridge MMC of auxiliary capacitor based on equality constraint is from all pressing topology, not only serve as multi-level voltage source current converter and directly apply to flexible direct-current transmission field, also can be by constituting STATCOM (STATCOM), Research on Unified Power Quality Conditioner (UPQC), the device such as THE UPFC (UPFC) is applied to flexible AC transmission field；Other application scenarios of this utility model topology of indirect utilization and thought are in interest field.