阅读说明：本技术 一种模块化多电平高压电磁发射电路 (Modularized multi-level high-voltage electromagnetic transmitting circuit ) 是由 李刚 张昕昊 于生宝 郭群 庞笑雨 秘家一 李超臣 于 2020-11-05 设计创作，主要内容包括：本发明属于地球物理探测中的电法探测仪器领域,尤其是适用于电法仪器的大功率高压逆变发射装置的一种模块化多电平高压电磁发射电路。发电机,产生380V、50Hz的三相交流电；通过三相整流桥以及隔离型DC/DC变换器,得到约500V的稳定直流电压,作为发射桥路的输入侧直流母线电压；发射桥路,采用MMC拓扑结构,采用驱动电路为发射桥路提供驱动信号,发射桥路为大地负载提供多电平稳定电压或电流；采用模块化设计,每级选用低电压器件,多级串联实现高电压输出,大大降低电压应力和开关损耗,具有拓扑结构简单、易于级联扩展、易于实现冗余控制等优点。(The invention belongs to the field of electrical detection instruments in geophysical exploration, and particularly relates to a modular multilevel high-voltage electromagnetic transmitting circuit which is suitable for a high-power high-voltage inversion transmitting device of an electrical instrument. The generator generates 380V and 50Hz three-phase alternating current; obtaining stable direct current voltage of about 500V as direct current bus voltage at the input side of the transmitting bridge circuit through a three-phase rectifier bridge and an isolated DC/DC converter; the transmitting bridge circuit adopts an MMC topological structure, adopts a driving circuit to provide a driving signal for the transmitting bridge circuit, and provides multi-level stable voltage or current for an earth load; the modular design is adopted, low-voltage devices are selected for each stage, high-voltage output is realized by multi-stage series connection, voltage stress and switching loss are greatly reduced, and the modular multi-stage high-voltage power supply has the advantages of simple topological structure, easiness in cascade expansion, easiness in realizing redundancy control and the like.)

1. A modular multilevel high voltage electromagnetic transmit circuit, the circuit comprising:

the generator generates 380V and 50Hz three-phase alternating current;

obtaining stable direct current voltage of about 500V as direct current bus voltage at the input side of the transmitting bridge circuit through a three-phase rectifier bridge and an isolated DC/DC converter;

the transmitting bridge circuit adopts an MMC topological structure, adopts a driving circuit to provide a driving signal for the transmitting bridge circuit, and provides multi-level stable voltage or current for an earth load; the transmitting bridge circuit comprises an a-phase p bridge arm, an a-phase n bridge arm, a B-phase p bridge arm and a B-phase n bridge arm, each bridge arm comprises a plurality of SM submodules connected in series, a connection point of the two bridge arms of the a-phase p bridge arm and the a-phase n bridge arm is used as an alternating current output end A, a connection point of the two bridge arms of the B-phase p bridge arm and the two bridge arms of the B-phase n bridge arm is used as an alternating current output end B, two points of the alternating current output end A and the alternating current output end B_ABAnd is connected with the earth load through a lead.

2. The circuit of claim 1, wherein the SM sub-module topology comprises an IGBT switching device S1, an IGBT switching device S2, a freewheeling diode D1, a freewheeling diode D2, and a capacitor C, the IGBT switching device S1 is connected in parallel with the freewheeling diode D1, the IGBT switching device S2 is connected in parallel with the freewheeling diode D2, the IGBT switching device S2 and the freewheeling diode D2 are connected in series and then connected in parallel with the capacitor C, a connection point M between the IGBT switching device S2 and the IGBT switching device S1 is provided, the other end point of the IGBT switching device S2 is a connection point P, and the connection point M and the connection point P serve as external ports of the half-bridge sub-module.

3. The circuit of claim 2, wherein the IGBT switching device S1 and the IGBT switching device S2 are driven by a drive circuit.

4. The circuit of claim 2, wherein the number of SM submodules invested in two phases is N, satisfying: n is a radical of_ap+N_an＝N_bp+N_bn＝N N_apAnd N_anThe number of sub-modules of an a-phase p bridge arm and an a-phase N bridge arm SM is N_bpAnd N_bnThe number of the sub-modules is p bridge arms of a phase b and n bridge arms of a phase b;

ud is input side direct current voltage, N SM submodule capacitor blocks input to each phase are connected in series for voltage division, and the capacitor voltage UC is

5. The circuit of claim 1, wherein the transmitter circuit outputs the output voltage U at multiple levels_ABIn the range of [ -U [ - ]_d，U_d]Ud is input side direct current voltage, N-1 levels are totally output, and the levels are output in sequence in one period T, namely U_dAnd N is the number of SM submodules input by two phases, and the implementation steps are as follows:

in thatIn the time period, 0 SM submodule is put into an a-phase p bridge arm, N SM submodules are put into an a-phase N bridge arm, N SM submodules are put into a B-phase p bridge arm, 0 SM submodule is put into a B-phase N bridge arm, the potential of a point A is 0, and the potential of a point B is NU_CAt an emission voltage of

U_AB＝U_A-U_B＝-NU_C＝-U_d

In thatIn the time period, a phase p bridge arm is put into 1 SM submodule, a phase N bridge arm is put into N-1 SM submodule, a phase p bridge arm is put into N-1 SM submodule, a phase N bridge arm is put into 1 SM submodule, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into 2 SM submodules, an a-phase N bridge arm is put into N-2 SM submodules, a b-phase p bridge arm is put into N-2 SM submodules, a b-phase N bridge arm is put into 2 SM submodules, and the potential of the point A is 2U_CThe potential at the point B is (N-2) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N-2 SM submodules, an a-phase N bridge arm is put into 2 SM submodules, a b-phase p bridge arm is put into 2 SM submodules, a b-phase N bridge arm is put into N-2 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N-1 SM submodules, an a-phase N bridge arm is put into 1 SM submodule, a b-phase p bridge arm is put into 1 SM submodule, a b-phase N bridge arm is put into N-1 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N SM submodules, an a-phase N bridge arm is put into 0 SM submodules, a b-phase p bridge arm is put into 0 SM submodules, a b-phase N bridge arm is put into N SM submodules, and the potential of an A point is NU_cThe potential at point B is 0, and the output voltage is

U_AB＝U_A-U_B＝NU_C＝U_d

In thatWithin a time period of eachIn a time period, ensuring that the total number of input submodules of each phase of two bridge arms is N, adjusting the number of the respective SM input submodules of the two phases of the p bridge arm and the N bridge arm, and outputting a voltage U_ABImplementation ofToIs output by the segment.

Technical Field

The invention belongs to the field of electrical detection instruments in geophysical exploration, and particularly relates to a modular multilevel high-voltage electromagnetic transmitting circuit of a high-power high-voltage inversion transmitting device suitable for electrical instruments.

Background

The development of energy and the utilization of resources are the basis of economic development, the rapid development of economy in recent years leads the demand of various countries on mineral resources to be increasingly increased, and deep detection is an effective way for solving the crisis of the mineral resources. An electromagnetic method instrument with an electric source for geophysical exploration needs to supply a transmitting current to an earth load, a primary pulse magnetic field is established underground, and the exploration depth is generally in positive correlation with the strength of a transmitting signal. In order to realize deep detection, an electromagnetic transmitting system with higher voltage and higher power needs to be developed on the basis of the existing transmitting system, and the technical level of detection equipment is improved.

The electromagnetic emission system is widely applied to a two-level inverter, when the output voltage level is higher, higher voltage stress and electromagnetic interference (EMI) exist, the requirement on a switching device is high, the switching frequency is high, the loss is large, the problems of heavy equipment weight, high cost and the like can be caused by a large heat dissipation system, and great difficulty is caused in field application of instruments. The common practice is to increase the voltage-bearing capacity by connecting a plurality of low-voltage switching devices in series, which reduces the cost to a certain extent, but has the problems of static and dynamic voltage sharing, and the voltage sharing circuit causes the problems of system complexity, loss increase, efficiency reduction and the like.

In order to avoid the above technical problems, in the 80 s of the 20 th century, a new idea of a novel inverter, namely a multi-level inverter, began to appear and received extensive attention. The multi-level inverter is optimized in a topological structure, the voltage stress is reduced by increasing the number of output levels, the switching tube works in a low-voltage and low-frequency state to reduce switching loss and EMI, the system inversion efficiency is high, and the multi-level inverter is more suitable for high-voltage and high-power application. Although the number of the switching devices is increased, the low-voltage low-frequency switching devices are selected, and the overall cost of the inverter is still reduced. The multi-level circuit topology mainly comprises a diode clamping type, a flying capacitor type and a cascade type, and in recent years, the multi-level technology is applied to an electromagnetic emission system. In patent No. CN103973147A, five-level inversion output of a diode-clamped transmitting circuit is realized, and the voltage on the IGBT is reduced to 1/2 of the dc bus voltage, thereby effectively increasing the output voltage. However, when the number of levels exceeds 5, the number of diodes and capacitors required increases sharply, and the topology becomes extremely complicated. In patent No. CN105375803A, a cascaded topology structure is adopted, so that cascaded H-bridge type five-level output is realized, and although the problem of voltage sharing of capacitors is avoided and the degree of modularization is high, an independent power supply is required under each module. As the number of levels increases, the dc power supply circuit becomes extremely complicated, and it is difficult to implement redundant control of the system.

Disclosure of Invention

The invention aims to provide a Modular Multilevel (MMC) -based high-voltage electromagnetic transmitting circuit. The modular design is adopted, low-voltage devices are selected for each stage, high-voltage output is realized by multi-stage series connection, voltage stress and switching loss are greatly reduced, and the modular multi-stage high-voltage power supply has the advantages of simple topological structure, easiness in cascade expansion, easiness in realizing redundancy control and the like.

The invention is realized in this way, a modular multilevel high-voltage electromagnetic emission circuit, the circuit includes:

the generator generates 380V and 50Hz three-phase alternating current;

obtaining stable direct current voltage of about 500V as direct current bus voltage at the input side of the transmitting bridge circuit through a three-phase rectifier bridge and an isolated DC/DC converter;

the transmitting bridge circuit adopts an MMC topological structure, adopts a driving and protecting circuit to provide a driving signal for the transmitting bridge circuit, and provides multi-level stable voltage or current for an earth load; wherein, the hairThe radio bridge circuit comprises an a-phase p bridge arm, an a-phase n bridge arm, a B-phase p bridge arm and a B-phase n bridge arm, each bridge arm comprises a plurality of SM submodules connected in series, the connection point of the a-phase p bridge arm and the a-phase n bridge arm is used as an alternating current output end A, the connection point of the B-phase p bridge arm and the B-phase n bridge arm is used as an alternating current output end B, the two points of the alternating current output end A and the alternating current output end B are used as output ends of a transmitting bridge circuit, the_ABAnd is connected with the earth load through a lead.

Further, the SM sub-module extension includes an IGBT switching device S1, an IGBT switching device S2, a freewheeling diode D1, a freewheeling diode D2, and a capacitor C, the IGBT switching device S1 is connected in parallel with the freewheeling diode D1, the IGBT switching device S2 is connected in parallel with the freewheeling diode D2, the IGBT switching device S2 is connected in parallel with the capacitor C after being connected in series, the IGBT switching device S2 is connected in parallel with the capacitor C at a connection point M of the IGBT switching device S1, the other end point of the IGBT switching device S2 is a connection point P, and the connection point M and the connection point P serve as external ports of the half-bridge.

Further, the IGBT switching device S1 and the IGBT switching device S2 are driven by a drive circuit.

Further, the number of SM submodules thrown into the two phases is N, and the following conditions are met: n is a radical of_ap+N_an＝N_bp+N_bn＝NN_apAnd N_anThe number of sub-modules of an a-phase p bridge arm and an a-phase N bridge arm SM is N_bpAnd N_bnThe number of the sub-modules is p bridge arms of a phase b and n bridge arms of a phase b;

ud is input side direct current voltage, N SM submodule capacitor blocks input to each phase are connected in series for voltage division, and the capacitor voltage UC is

Further, the transmitting circuit outputs the output voltage U at multiple levels_ABIn the range of [ -U [ - ]_d，U_d]Ud is input side direct current voltage, N-1 levels are totally output, and the levels are output in sequence in one period T, namelyN isThe number of SM submodules which are input in two phases is as follows:

in thatIn the time period, 0 SM submodule is put into an a-phase p bridge arm, N SM submodules are put into an a-phase N bridge arm, N SM submodules are put into a B-phase p bridge arm, 0 SM submodule is put into a B-phase N bridge arm, the potential of a point A is 0, and the potential of a point B is NU_CAt an emission voltage of

U_AB＝U_A-U_B＝-NU_C＝-U_d

In thatIn the time period, a phase p bridge arm is put into 1 SM submodule, a phase N bridge arm is put into N-1 SM submodule, a phase p bridge arm is put into N-1 SM submodule, a phase N bridge arm is put into 1 SM submodule, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into 2 SM submodules, an a-phase N bridge arm is put into N-2 SM submodules, a b-phase p bridge arm is put into N-2 SM submodules, a b-phase N bridge arm is put into 2 SM submodules, and the potential of the point A is 2U_CThe potential at the point B is (N-2) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N-2 SM submodules, an a-phase N bridge arm is put into 2 SM submodules, a b-phase p bridge arm is put into 2 SM submodules, and a b-phaseN bridge arms are put into N-2 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N-1 SM submodules, an a-phase N bridge arm is put into 1 SM submodule, a b-phase p bridge arm is put into 1 SM submodule, a b-phase N bridge arm is put into N-1 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

In thatIn the time period, an a-phase p bridge arm is put into N SM submodules, an a-phase N bridge arm is put into 0 SM submodules, a b-phase p bridge arm is put into 0 SM submodules, a b-phase N bridge arm is put into N SM submodules, and the potential of an A point is NU_cThe potential at point B is 0, and the output voltage is

U_AB＝U_A-U_B＝NU_C＝U_d

In thatWithin a time period of eachIn a time period, ensuring that the total number of input submodules of each phase of two bridge arms is N, adjusting the number of the respective SM input submodules of the two phases of the p bridge arm and the N bridge arm, and outputting a voltage U_ABImplementation ofToIs output by the segment.

Compared with the prior art, the invention has the beneficial effects that:

series expansion and redundancy design can be realized by setting the number N of the SM submodules connected in series with each bridge arm.

The transmitting bridge circuit adopts a modular multilevel topological structure, the voltage and du/dt borne by the switching tube of each SM submodule depends on the capacitance voltage connected with the switching tube in parallel in the SM submodule, and the voltage stress is the direct-current bus voltageThe high-voltage electromagnetic emission system has the advantages of small du/dt, small EMI (electro-magnetic interference), high inversion efficiency, simple topological structure, high modularization degree, easiness in cascade expansion and redundancy control, can achieve the purpose of high-voltage and high-power output by using low-voltage-withstanding and low-power devices, and is suitable for high-voltage electromagnetic emission systems.

Drawings

FIG. 1 is a block diagram of a high-voltage electromagnetic emission system;

FIG. 2 is a block diagram of a modular multilevel transmit bridge;

FIG. 3 is a diagram of an SM sub-module topology;

FIG. 4 is a schematic diagram of an equivalent model of a modular multilevel transmit bridge;

fig. 5 is an N-level output waveform diagram.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, a block diagram of a high-voltage electromagnetic emission system according to the present invention is shown in fig. 1. The system comprises a generator, a direct current power supply, an MMC transmitting bridge circuit and an earth load.

The generator generates 380V and 50Hz three-phase alternating current;

obtaining stable direct current voltage of about 500V as direct current bus voltage at the input side of the transmitting bridge circuit through a three-phase rectifier bridge and an isolated DC/DC converter;

the transmitting bridge circuit adopts an MMC topological structure, adopts a driving circuit to provide a driving signal for the transmitting bridge circuit, and provides multi-level stable voltage or current for an earth load; the transmitting bridge circuit comprises an a-phase p bridge arm, an a-phase n bridge arm, a B-phase p bridge arm and a B-phase n bridge arm, each bridge arm comprises a plurality of SM submodules connected in series, a connection point of the two bridge arms of the a-phase p bridge arm and the a-phase n bridge arm is used as an alternating current output end A, a connection point of the two bridge arms of the B-phase p bridge arm and the two bridge arms of the B-phase n bridge arm is used as an alternating current output end B, two points of the alternating current output end A and the alternating current output end B_ABAnd is connected with the earth load through a lead.

The structure of the modular multilevel transmission bridge proposed by the present invention is shown in fig. 2, and the transmission bridge comprises 4N half-bridge sub-modules (SM) and loads R and L. The basic framework of the transmitting bridge circuit is that an a phase and a b phase are connected in parallel, each phase is formed by connecting a p bridge arm and an n bridge arm in series, 4 bridge arms are provided in total, and the p bridge arm, the n bridge arm, the p bridge arm and the n bridge arm of the b phase including the a phase are respectively represented as ap, an, bp and bn. Each bridge arm is formed by connecting N SM submodules in series, and the SM submodules of the a-phase p-bridge arm are respectively SM_a1、SM_a2、...、SM_aNThe SM submodules of the a-phase n bridge arm are respectively SM_1a、SM_2a、...、SM_NaThe SM submodules of the b-phase p bridge arm are respectively SM_b1、SM_b2、...、SM_bNThe SM submodules of the b-phase n bridge arm are respectively SM_1b、SM_2b、...、SM_Nb. and the connection point of the two bridge arms of the a-phase p bridge arm and the a-phase n bridge arm is used as an alternating current output end A, and the connection point of the two bridge arms of the B-phase p bridge arm and the B-phase n bridge arm is used as an alternating current output end B. A. The two points B are used as the output ends of the transmitting bridge circuit and are connected with an earth load (R is an earth resistive load, and L is an earth inductive load) through a lead.

The SM submodule topological structure provided by the invention is shown in FIG. 3, and mainly comprises 2 IGBT switching devices S1, an IGBT switching device S2, a freewheeling diode D1, a freewheeling diode D2 and a capacitor C. IGBT switchDevice S₁And a freewheeling diode D₁Parallel, IGBT switching device S₂And a freewheeling diode D₂And the two are connected in parallel, and then connected in parallel with the capacitor C after being connected in series. IGBT switching device S₂And IGBT switching device S₁M, IGBT switching device S₂The other end point is P. M, P serve as external ports for the half-bridge sub-modules.

Fig. 1 is a block diagram of a high-voltage electromagnetic emission system. The generator generates 380V and 50Hz three-phase alternating current, and stable direct current voltage of about 500V is obtained through a three-phase rectifier bridge and an isolated DC/DC converter and is used as direct current bus voltage at the input side of the transmitting bridge circuit. The transmitting bridge circuit adopts an MMC topological structure, the driving circuit provides driving signals for the IGBTs in each SM submodule of the transmitting bridge circuit, and the transmitting bridge circuit provides multi-level stable voltage or current for an earth load so as to meet the requirement of forming a primary magnetic field of electromagnetic detection.

See fig. 2 for a modular multilevel transmit bridge architecture. N is a radical of_apAnd N_anThe number of sub-modules for the two bridge arms of the a-phase p bridge arm and the a-phase N bridge arm, N_bpAnd N_bnThe number of sub-modules for inputting two bridge arms of a b-phase p bridge arm and a b-phase n bridge arm is U_AIs the voltage at A point of the a-phase AC output, U_BIs the voltage at B point of the B AC output terminal, U_ABThe voltage output by the transmitting bridge is applied across the earth load. At any time, the number of half-bridge sub-modules which are put into a phase and a phase is N, namely

N_pa+N_na＝N_pb+N_nb＝N (1)

U_dFor inputting side DC voltage, N sub-module capacitor blocks inputted to each phase are connected in series for voltage division, and the capacitor voltage U_CIs composed of

Fig. 3 is a SM sub-module topology. U shape_SMFor sub-module port voltage, U_CFor capacitor voltage, by switching devices S on or off IGBT₁IGBT switching device S₂So that each submodule can workIn the on or off state, the relationship between the sub-module port voltage and the switch state is shown in table 1. IGBT switching device S₁Conducting IGBT switching device S₂When the module is turned off, the sub-module works in the on state, and the voltage U of the sub-module port_SM＝U_C(ii) a IGBT switching device S₁Turn-off, IGBT switching device S₂When the module is conducted, the sub-module works in a cut-off state, and the voltage U of the sub-module port_SM0. The relationship between the port voltage and the switch state of the SM submodule is shown in the table 1(1 represents that the switch tube is conducted, and 0 represents that the switch tube is turned off).

TABLE 1 SM submodule port Voltage to switch State relationship

USM	S1	S2
			0	0	1
UC	1	0

The realization method of the invention is as follows:

fig. 4 is an equivalent model of a modular multilevel transmit bridge. IGBT switching device S of each SM submodule₁IGBT switching device S₂Can be equivalent to a change-over switch S connected with a suspension capacitor C in parallel, each SM submodule can be equivalent to the parallel connection of the change-over switch S and the suspension capacitor C, and the transmitting bridge routes 4N SM submodulesAnd forming a module equivalent circuit. The equivalent circuit of the transmitting bridge circuit has 4N switching switches S including a-phase SM_a1、SM_a2、...、SM_aNChange-over switch S for submodules_a1、S_a2、...、S_aNPhase a SM_1a、SM_2a、...、SM_NaChange-over switch S for submodules_1a、S_2a、...、S_NaB phase SM_b1、SM_b2、...、SM_bNChange-over switch S for submodules_b1、S_b2、...、S_bNB phase SM_1b、SM_2b、...、SM_NbChange-over switch S for submodules_1b、S_2b、...、S_Nb. By controlling the change-over switch S of each SM submodule, the SM submodule can be controlled to be in a switching-in state or a switching-off state. When the SM submodule works in an on state, the voltage of the submodule port is U_C(ii) a When the submodule works in the cutting-off state, the voltage of the submodule port is 0. SM submodule capacitor voltage U with each bridge arm voltage as input_CThe sum of the series connection, the potential at the point A and the point B and the output voltage are

By controlling the equivalent change-over switch S of each SM submodule and setting the number of bridge arms connected into the series SM submodules, multi-level output can be realized. Output voltage U_ABThe relationship between the number of SM charged into each arm is shown in table 2.

TABLE 2 relationship between output voltage and input SM number of each bridge arm

The multi-level output waveform is shown in FIG. 5, the output voltage U_ABIn the range of [ -U [ - ]_d，U_d]There are N-1 levels in total, and the levels are output in order within one period T, respectively The method comprises the following implementation steps:

(1) in thatIn the time period, 0 SM submodule is put into an a-phase p bridge arm, N SM submodules are put into an a-phase N bridge arm, N SM submodules are put into a B-phase p bridge arm, 0 SM submodule is put into a B-phase N bridge arm, the potential of a point A is 0, and the potential of a point B is NU_CAt an emission voltage of

U_AB＝U_A-U_B＝-NU_C＝-U_d (4)

(2) In thatIn the time period, a phase p bridge arm is put into 1 SM submodule, a phase N bridge arm is put into N-1 SM submodule, a phase p bridge arm is put into N-1 SM submodule, a phase N bridge arm is put into 1 SM submodule, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

(3) In thatIn the time period, an a-phase p bridge arm is put into 2 SM submodules, an a-phase N bridge arm is put into N-2 SM submodules, a b-phase p bridge arm is put into N-2 SM submodules, a b-phase N bridge arm is put into 2 SM submodules, and the potential of the point A is 2U_CThe potential at the point B is (N-2) U_COutput voltage of

(4) In thatIn the time period, an a-phase p bridge arm is put into N-2 SM submodules, an a-phase N bridge arm is put into 2 SM submodules, a b-phase p bridge arm is put into 2 SM submodules, a b-phase N bridge arm is put into N-2 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

(5) In thatIn the time period, an a-phase p bridge arm is put into N-1 SM submodules, an a-phase N bridge arm is put into 1 SM submodule, a b-phase p bridge arm is put into 1 SM submodule, a b-phase N bridge arm is put into N-1 SM submodules, and the potential of the point A is U_CThe potential at the point B is (N-1) U_COutput voltage of

(4) In thatIn the time period, an a-phase p bridge arm is put into N SM submodules, an a-phase N bridge arm is put into 0 SM submodules, a b-phase p bridge arm is put into 0 SM submodules, a b-phase N bridge arm is put into N SM submodules, and the potential of an A point is NU_cThe potential at point B is 0, and the output voltage is

U_AB＝U_A-U_B＝NU_C＝U_d (9)

(5) In thatWithin a time period of eachIn a time period, the total number of input submodules of each phase of two bridge arms is ensured to be N, the number of the respective SM input submodules of the two phases of p and N bridge arms is adjusted, and a voltage U is output_ABCan realizeToSimilar to the above process, the segmentation output of (1) will not be described in detail herein.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.