WO2021179707A1 - Multi-phase soft charging control method and system for multi-level direct-current solid-state transformer - Google Patents

Multi-phase soft charging control method and system for multi-level direct-current solid-state transformer Download PDF

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Publication number
WO2021179707A1
WO2021179707A1 PCT/CN2020/134878 CN2020134878W WO2021179707A1 WO 2021179707 A1 WO2021179707 A1 WO 2021179707A1 CN 2020134878 W CN2020134878 W CN 2020134878W WO 2021179707 A1 WO2021179707 A1 WO 2021179707A1
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bridge arm
sub
mmc
primary side
side mmc
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PCT/CN2020/134878
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French (fr)
Chinese (zh)
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唐德平
赵涛
缪靖宇
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合肥科威尔电源系统股份有限公司
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Publication of WO2021179707A1 publication Critical patent/WO2021179707A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/36—Means for starting or stopping converters
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements

Definitions

  • the invention belongs to the technical field of power electronics, and specifically relates to a multi-stage soft charging control method and system for a multi-level DC solid-state transformer.
  • Modular multilevel DC solid-state transformers can not only realize the transformation, isolation and energy conversion functions of traditional transformers, but also have the advantages of simple control, high scalability, and realization of primary and secondary fault isolation. It has received wide attention from scholars at home and abroad.
  • a modular multi-level DC solid-state transformer and its charging control method discloses a modular multi-level DC solid-state transformer and its charging control method.
  • the transformer includes two sets of MMC, high-frequency transformer, resistors and switches.
  • One set of MMC is connected to the primary side of the high-frequency transformer, and the other set of MMC is connected to the secondary side of the high-frequency transformer.
  • the primary side MMC is connected through a parallel structure of resistors and switches. Connect the DC power supply, and connect the MMC on the secondary side to the load.
  • This method first inputs all 2N sub-modules of each phase of the primary side MMC of the DC transformer, and then reduces the number of primary side MMC sub-modules by comparing the primary side DC current value with the limited current value, and finally the number of sub-modules input to each phase Redistribute the upper and lower bridge arms and determine the trigger pulse of the MMC on the primary side in combination with the phase shift angle to realize the soft charging of the DC transformer.
  • the above-mentioned invention patent application only performs closed-loop control on the secondary side.
  • the current impact during the charging process of the primary side is controlled in an open-loop manner.
  • the magnitude and time of the inrush current are uncontrollable, and the dynamic performance is poor, resulting in more modular power.
  • the flat DC solid-state transformer will still generate a large current spike on the AC side and DC side of the system when it is started, which will easily cause damage to the power semiconductor devices and high-frequency transformers in the sub-modules, and will shorten the service life of the capacitors. Conducive to the safe operation of the system.
  • the technical problem to be solved by the present invention is how to reduce the problem of current spikes on the AC side and the DC side when the modular multilevel DC solid-state transformer is started.
  • the present invention solves the above technical problems through the following technical solutions: a multi-stage soft charging control method for a multi-level DC solid-state transformer.
  • the modular multi-level DC solid-state transformer includes an input source Vdc1, an output source Vdc2, and a single Side MMC, secondary side MMC, current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes multiple sub-modules SM An H-bridge circuit is formed; the secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd After being connected in parallel with the current-limiting switch S d , one end is connected to the primary side MMC, and the other end is connected to the input source Vdc1; the input source Vdc1 is a direct
  • the multi-stage soft charging control method includes: stage one, the sub-module SM of the primary side MMC does not control charging; stage two: using the peak current to control the soft charging of the sub-module SM of the primary side MMC; stage three: using phase-shift modulation control The sub-module SM of the secondary side MMC is soft charged.
  • the above-mentioned multi-stage soft charging control method is applied to a modular multi-level DC solid-state transformer, and different soft charging strategies are adopted at different stages to realize the rapid and stable charging of the sub-module capacitance of the modular multi-level DC solid-state transformer, and reduce This reduces the current spikes on the AC side and the DC side when the transformer is started, protects the power devices and high-frequency transformers in the sub-modules, increases the service life of the capacitors, and greatly facilitates the safe operation of the system.
  • the sub-module SM includes a first power switch tube (S 1 ), a second power switch tube (S 2 ), a parallel capacitor C, a first anti-parallel diode (VD 1 ), The second anti-parallel diode (VD 2 ); the first power switch tube (S 1 ) and the second power switch tube (S 2 ) form a half-bridge structure; the first anti-parallel diode (VD 1 ) is connected in anti-parallel Two ends of a power switch (S 1 ); a second anti-parallel diode (VD 2 ) is connected in anti-parallel to both ends of the second power switch (S 2 ); the parallel capacitor C is connected in parallel to the half-bridge structure Both ends; the midpoint of the half-bridge structure is used as the input end of the sub-module SM.
  • the sub-module SM has two working states:
  • the driving pulse of the first power switch tube (S 1 ) in the sub-module SM is 0 throughout the switching period, and the driving pulse of the second power switch tube (S 2 ) is the duty cycle Is the PWM signal wave of D; the duty ratio D is the proportion of the time required for the average value of the primary side bridge arm current to rise from the initial value of the cycle to the given peak value of the primary side bridge arm current.
  • the first stage is specifically:
  • the second stage is specifically:
  • i 1 0.5(i a +i b )
  • stage three is specifically as follows:
  • the nominal voltage (V 1 * ) of the primary side capacitor is calculated according to the following formula:
  • V 1 * the nominal voltage of the primary side capacitor
  • V dc1 is the voltage of the input source
  • M is the number of sub-modules SM per half bridge arm of the primary side MMC.
  • the nominal voltage (V 2 * ) of the secondary side capacitor is calculated according to the following formula:
  • V 2 * the nominal voltage of the primary side capacitor
  • V dc2 is the voltage of the output source
  • N is the number of sub-modules SM per half bridge arm of the secondary side MMC.
  • a multi-stage soft charging control system for a multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, a secondary side MMC, and a current-limiting resistor R d , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the secondary MMC-side sub-module SM comprises a plurality of H-bridge circuit configuration; the primary side and the secondary side MMC MMC connected by high-frequency transformer T; after the current limiting resistor R d and S d limiting switch in parallel with the first end The other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output
  • the multi-stage soft charging control system includes: module one, the sub-module SM of the primary side MMC does not control the charging module; module two: using the peak current to control the sub-module SM soft charging module of the primary side MMC; module three: using phase shifting Modulate and control the sub-module SM soft charging module of the secondary side MMC.
  • the primary side MMC further includes a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm of the primary side MMC constitute an H bridge structure;
  • the first bridge arm of the primary side MMC includes an upper half bridge arm and a lower half bridge arm;
  • the second bridge arm of the primary side MMC also includes an upper half bridge arm and a lower half bridge arm;
  • the upper half of the first bridge arm of the primary side MMC includes M sub-modules SM and an inductance La1 on the first bridge arm, and the M sub-modules SM and an inductance La1 on the first bridge arm are in turn series; lower half bridge arm of the first arm of the primary side of the MMC comprises M sub-module SM and the inductor L a2 next first bridge arm, the first arm of a half bridge arm lower side of the MMC
  • the structure of is symmetrical with the structure of the upper half of the first bridge arm of the primary side MMC; the symmetry point is point a;
  • the upper half of the second bridge arm of the primary side MMC includes M sub-modules SM and an inductance L b1 on the second bridge arm.
  • the M sub-modules SM and the inductance L b1 on the second bridge arm are in turn In series;
  • the lower half of the second leg of the primary side MMC includes M submodules SM and a second lower inductance L b2 , the lower half of the second leg of the primary side MMC
  • the structure of is symmetrical with the structure of the upper half of the second bridge arm of the primary side MMC; the symmetry point is point b;
  • the secondary side MMC includes a third bridge arm and a fourth bridge arm; the third bridge arm and the fourth bridge arm of the secondary side MMC constitute an H bridge structure;
  • the third bridge arm of the secondary side MMC includes an upper half bridge arm and a lower half bridge arm;
  • the fourth bridge arm of the secondary side MMC also includes an upper half bridge arm and a lower half bridge arm;
  • the upper half of the third bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L c1 on the third bridge arm, the N sub-modules SM and an inductance L c1 on the third bridge arm
  • the lower half of the third bridge arm of the secondary side MMC includes N sub-modules SM and a lower inductance L c2 of the third bridge arm
  • the lower half of the third bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the third bridge arm of the secondary side MMC; the symmetry point is point c;
  • the upper half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L d1 on the fourth bridge arm, the N sub-modules SM and an inductance L d1 on the fourth bridge arm
  • the lower half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and a fourth bridge arm lower inductance L d2 , the lower half of the fourth bridge arm of the secondary side MMC
  • the structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the fourth bridge arm of the secondary side MMC; the symmetry point is point d;
  • the four terminals of the high-frequency transformer T are respectively connected to point a, point b, point c, and point d.
  • the multi-stage soft charging control method of the present invention is applied to a modular multi-level DC solid-state transformer, and different soft charging strategies are adopted at different stages to realize the rapid, rapid, and rapid, Stable charging reduces the current spikes on the AC side and DC side when the transformer is started, protects the power devices and high-frequency transformers in the sub-modules, increases the service life of the capacitors, and greatly benefits the safe operation of the system.
  • Fig. 1 is a topology diagram of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
  • Fig. 2 is a schematic diagram of a multi-stage soft charging control method of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
  • Fig. 3 is a flowchart of a multi-stage soft charging control method of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
  • Fig. 4 is a structural diagram of a modular multi-level DC solid-state transformer sub-module according to an embodiment of the present invention.
  • Fig. 5 is a driving waveform diagram of a modular multi-level direct current solid-state transformer sub-module working in a locked state according to an embodiment of the present invention.
  • Fig. 6 is a driving waveform diagram of a modular multi-level direct current solid-state transformer sub-module working in a bypass state according to an embodiment of the present invention.
  • the modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC.
  • the primary-side MMC includes multiple sub-modules SM to form an H-bridge circuit
  • the secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd and the current-limiting switch S d After parallel connection, one end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source Or the load is connected to the output end of the secondary side MMC.
  • the described multi-stage soft charging control method includes: stage one, the sub-module SM of the primary side MMC does not control charging; stage two: using the peak current to control the sub-module SM of the primary side MMC soft charging ; Phase 3: Use phase-shift modulation to control the soft charging of the sub-module SM of the secondary side MMC.
  • the sub-module SM includes a first power switch S 1 , a second power switch S 2 , a parallel capacitor C, a first anti-parallel diode VD 1 , and a second anti-parallel diode VD 2 ;
  • the first power switch tube S 1 and the second power switch tube S 2 described above constitute a half-bridge structure;
  • the first anti-parallel diode VD 1 is connected in anti-parallel to both ends of the first power switch tube S 1 ;
  • the second anti-parallel diode VD 2 is anti-parallel connected in parallel across the second power switch S 2; ends of the parallel capacitor C connected in parallel with the half-bridge; the midpoint of the half-bridge configuration as the input terminal of the SM module.
  • the sub-module SM has two working states:
  • the driving pulse of the first power switch S 1 in the sub-module SM is 0 during the entire switching period, and the driving pulse of the second power switch S 2 is a PWM with a duty cycle of D Signal wave; the duty cycle D is the ratio of the time required for the average value of the primary side bridge arm current to rise from the initial value of the cycle to the given peak value of the primary side bridge arm current.
  • the first stage is specifically:
  • the path of the charging current of the first leg of the primary side MMC is: V dc1 positive ⁇ R d ⁇ VD11 ⁇ C11 ⁇ L a1 ⁇ L a2 ⁇ VD13 ⁇ C13 ⁇ V dc1 negative;
  • the path of the charging current of the second leg of the primary side MMC is: V dc1 positive ⁇ R d ⁇ VD21 ⁇ C12 ⁇ L b1 ⁇ L b2 ⁇ VD23 ⁇ C14 ⁇ V dc1 negative.
  • the nominal voltage V 1 * of the primary side capacitor is calculated according to the following formula:
  • V 1 * the nominal voltage of the primary-side capacitor
  • V dc1 is the voltage of the input source
  • M is the number of sub-modules SM per half-bridge arm of the primary-side MMC.
  • the second stage is specifically:
  • i 1 0.5(i a +i b )
  • the stage three is specifically:
  • the first power switching tube S 1 of all sub-modules SM of the two bridge arms of the primary side MMC is turned off during the entire cycle, and the second power switching tube S 2 of all the sub-modules SM of the two bridge arms of the primary side MMC adopts phase shifting. Modulation; all sub-modules SM of the secondary side MMC are working in a locked state;
  • the nominal voltage V 2 * of the secondary side capacitor is calculated according to the following formula:
  • V 2 * the nominal voltage of the primary side capacitor
  • V dc2 is the voltage of the output source
  • N is the number of sub-modules SM per half bridge arm of the secondary side MMC.
  • the freewheeling path of the primary side MMC current is: S12 ⁇ L a1 ⁇ L s ⁇ L b1 ⁇ VD22 ⁇ S12; at this time, the power transmitted from the primary side MMC to the secondary MMC is zero.
  • the primary-side MMC current flow path is: V dc1 positive ⁇ S12 ⁇ L a1 ⁇ L s ⁇ L b2 ⁇ S24 ⁇ V dc1 negative;
  • the primary side MMC current flow path is: V dc1 positive ⁇ S22 ⁇ L b1 ⁇ L s ⁇ La2 ⁇ S14 ⁇ V dc1 negative.
  • the charging current path of the secondary side sub-module is divided into two paths, and the capacitor C22 and the capacitor C23 are charged at the same time;
  • the path for charging the capacitor C22 is: point c ⁇ L c1 ⁇ VD32 ⁇ VD41 ⁇ C22 ⁇ L d1 ⁇ point d;
  • the path to charge the capacitor C23 is: point c ⁇ L c2 ⁇ VD33 ⁇ C23 ⁇ VD44 ⁇ L d2 ⁇ point d;
  • the charging current path of the secondary side sub-module is divided into two paths, and the capacitor C21 and the capacitor C24 are charged at the same time;
  • the path for charging the capacitor C21 is: point d ⁇ L d1 ⁇ VD42 ⁇ VD31 ⁇ C21 ⁇ L c1 ⁇ point c;
  • the path to charge the capacitor C24 is: point d ⁇ L d2 ⁇ VD43 ⁇ C24 ⁇ VD34 ⁇ L c2 ⁇ point c.
  • a multi-stage soft charging control system for a multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC.
  • the primary-side MMC includes multiple sub-modules SM to form an H-bridge circuit
  • the secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd and the current-limiting switch S d After parallel connection, one end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source Or the load is connected to the output end of the secondary side MMC.
  • the multi-stage soft charging control system includes: module one, the sub-module SM of the primary side MMC does not control the charging module; module two: using the peak current to control the sub-module SM soft charging module of the primary side MMC; module three: using phase shifting Modulate and control the sub-module SM soft charging module of the secondary side MMC.
  • the primary side MMC further includes a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm of the primary side MMC constitute an H bridge structure.
  • the first bridge arm of the primary side MMC includes an upper half bridge arm and a lower half bridge arm; the second bridge arm of the primary side MMC also includes an upper half bridge arm and a lower half bridge arm.
  • the upper half of the first bridge arm of the primary side MMC includes M sub-modules SM and an inductance La1 on the first bridge arm, and the M sub-modules SM and an inductance La1 on the first bridge arm are in turn series; lower half bridge arm of the first arm of the primary side of the MMC comprises M sub-module SM and the inductor L a2 next first bridge arm, the first arm of a half bridge arm lower side of the MMC
  • the structure of is symmetrical with the structure of the upper half of the first bridge arm of the primary side MMC; the symmetry point is point a.
  • the upper half of the second bridge arm of the primary side MMC includes M sub-modules SM and an inductance L b1 on the second bridge arm.
  • the M sub-modules SM and the inductance L b1 on the second bridge arm are in turn In series;
  • the lower half of the second leg of the primary side MMC includes M submodules SM and a second lower inductance L b2 , the lower half of the second leg of the primary side MMC
  • the structure of is symmetrical with the structure of the upper half of the second bridge arm of the primary side MMC; the symmetry point is point b.
  • the secondary side MMC includes a third bridge arm and a fourth bridge arm; the third bridge arm and the fourth bridge arm of the secondary side MMC constitute an H bridge structure.
  • the third bridge arm of the secondary side MMC includes an upper half bridge arm and a lower half bridge arm; the fourth bridge arm of the secondary side MMC also includes an upper half bridge arm and a lower half bridge arm.
  • the upper half of the third bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L c1 on the third bridge arm, the N sub-modules SM and an inductance L c1 on the third bridge arm
  • the lower half of the third bridge arm of the secondary side MMC includes N sub-modules SM and a lower inductance L c2 of the third bridge arm
  • the lower half of the third bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the third bridge arm of the secondary side MMC; the symmetry point is point c.
  • the upper half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L d1 on the fourth bridge arm, the N sub-modules SM and an inductance L d1 on the fourth bridge arm In series; the lower half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and a fourth bridge arm lower inductance L d2 , the lower half of the fourth bridge arm of the secondary side MMC
  • the structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the fourth bridge arm of the secondary side MMC; the symmetry point is point d.
  • the four terminals of the high-frequency transformer T are respectively connected to point a, point b, point c, and point d.

Abstract

A multi-phase soft charging control method and system for a multi-level direct current (DC) solid state transformer, which relate to the technical field of electricity and electronics, and solve the problem of how to reduce current spikes at the alternating current (AC) side and the DC side when a modular multi-level DC solid state transformer starts. The multi-phase soft charging control method comprises: charging a submodule (SM) at the primary side MMC without control; using a peak current to control soft charging of the submodule (SM) at the primary side MMC; and using phase shift modulation to control the soft charging of the submodule (SM) at the secondary side MMC. The control system comprises: an input source (Vdc1), an output source (Vdc2), a primary side MMC, a secondary side MMC, a current limiting resistor (Rd), a current limiting switch (Sd), and a high-frequency transformer (T). The control method achieves rapid and stable charging of a capacitor (C) of a submodule (SM) of a modular multi-level DC solid state transformer, reduces the current spikes at the AC side and the DC side when the transformer starts, protects the power devices (S1, S2) and the high-frequency transformer (T) in the submodules (SM), improves the service life of the capacitor (C), and favors the safe operation of the system.

Description

一种多电平直流固态变压器多阶段软充控制方法及系统Multi-stage soft charging control method and system for multi-level direct current solid-state transformer 技术领域Technical field
本发明属于电力电子技术领域，具体涉及一种多电平直流固态变压器多阶段软充控制方法及系统。The invention belongs to the technical field of power electronics, and specifically relates to a multi-stage soft charging control method and system for a multi-level DC solid-state transformer.
背景技术Background technique
为了保护环境以及响应国家可持续发展的理念，新能源在日常生活中的使用比重越来越大，如何解决新能源发电后的电力传输问题非常关键。传统的变压器具有重量和体积大、存在谐波污染，以及维护相对困难等缺点不再适用于新能源的电力传输问题。In order to protect the environment and respond to the country's concept of sustainable development, new energy is used more and more in daily life. How to solve the problem of power transmission after new energy generation is very important. Traditional transformers have the disadvantages of large weight and volume, harmonic pollution, and relatively difficult maintenance, and are no longer suitable for new energy power transmission problems.
模块化多电平直流固态变压器(modular multilevel converter，简称MMC)除了能实现传统变压器的变压、隔离和能量转换功能外，还具有控制简单、可拓展性高、实现原副边故障隔离等优点而受到国内外学者的广泛关注。Modular multilevel DC solid-state transformers (MMC for short) can not only realize the transformation, isolation and energy conversion functions of traditional transformers, but also have the advantages of simple control, high scalability, and realization of primary and secondary fault isolation. It has received wide attention from scholars at home and abroad.
申请号为201810464040.X的中国发明专利申请《一种模块化多电平直流固态变压器及其充电控制方法》，公开一种模块化多电平直流固态变压器及其充电控制方法。该变压器包括两组MMC、高频变压器、电阻和开关，其中一组MMC连接高频变压器的原边，另一组MMC连接高频变压器的副边，原边侧MMC通过电阻和开关的并联结构连接直流电源，副边侧的MMC连接负载。该方法首先将直流变压器原边MMC每相所有2N个子模块投入，然后通过比较原边直流电流值与限定电流值的大小减少原边MMC子模块投入的 数量，最后对每相投入的子模块数量在上下桥臂重新分配，并结合移相角确定原边MMC两的触发脉冲，实现直流变压器软充电。The Chinese invention patent application with the application number 201810464040.X "A modular multi-level DC solid-state transformer and its charging control method" discloses a modular multi-level DC solid-state transformer and its charging control method. The transformer includes two sets of MMC, high-frequency transformer, resistors and switches. One set of MMC is connected to the primary side of the high-frequency transformer, and the other set of MMC is connected to the secondary side of the high-frequency transformer. The primary side MMC is connected through a parallel structure of resistors and switches. Connect the DC power supply, and connect the MMC on the secondary side to the load. This method first inputs all 2N sub-modules of each phase of the primary side MMC of the DC transformer, and then reduces the number of primary side MMC sub-modules by comparing the primary side DC current value with the limited current value, and finally the number of sub-modules input to each phase Redistribute the upper and lower bridge arms and determine the trigger pulse of the MMC on the primary side in combination with the phase shift angle to realize the soft charging of the DC transformer.
但是上述发明专利申请只是对副边进行闭环控制，对于原边充电过程中的电流冲击是通过开环的方式进行控制的，冲击电流的大小和时间不可控，动态性能差，导致模块化多电平直流固态变压器在启动时会在系统的交流侧与直流侧仍然会产生很大的电流尖峰，容易造成子模块中功率半导体器件和高频变压器的损坏，还会减短电容的使用寿命，不利于系统的安全运行。However, the above-mentioned invention patent application only performs closed-loop control on the secondary side. The current impact during the charging process of the primary side is controlled in an open-loop manner. The magnitude and time of the inrush current are uncontrollable, and the dynamic performance is poor, resulting in more modular power. The flat DC solid-state transformer will still generate a large current spike on the AC side and DC side of the system when it is started, which will easily cause damage to the power semiconductor devices and high-frequency transformers in the sub-modules, and will shorten the service life of the capacitors. Conducive to the safe operation of the system.
发明内容Summary of the invention
本发明所要解决的技术问题在于如何减小模块化多电平直流固态变压器启动时交流侧和直流侧电流尖峰的问题。The technical problem to be solved by the present invention is how to reduce the problem of current spikes on the AC side and the DC side when the modular multilevel DC solid-state transformer is started.
本发明是通过以下技术方案解决上述技术问题的：一种多电平直流固态变压器多阶段软充控制方法，所述的模块化多电平直流固态变压器，包括输入源Vdc1，输出源Vdc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源Vdc1连接；所述的输入源Vdc1为直流源；输入源Vdc1给一次侧MMC供电；所述的输出源Vdc2为直流源或负载连接在二次侧MMC的输出端； The present invention solves the above technical problems through the following technical solutions: a multi-stage soft charging control method for a multi-level DC solid-state transformer. The modular multi-level DC solid-state transformer includes an input source Vdc1, an output source Vdc2, and a single Side MMC, secondary side MMC, current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes multiple sub-modules SM An H-bridge circuit is formed; the secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd After being connected in parallel with the current-limiting switch S d , one end is connected to the primary side MMC, and the other end is connected to the input source Vdc1; the input source Vdc1 is a direct current source; the input source Vdc1 supplies power to the primary side MMC; the output source Vdc2 is a direct current The source or load is connected to the output terminal of the secondary side MMC;
所述的多阶段软充控制方法包括：阶段一，一次侧MMC的子模块SM不控充电；阶段二：使用峰值电流控制一次侧MMC的子模块SM软充电；阶段三：使用移相调制控制二次侧MMC的子模块SM软充电。The multi-stage soft charging control method includes: stage one, the sub-module SM of the primary side MMC does not control charging; stage two: using the peak current to control the soft charging of the sub-module SM of the primary side MMC; stage three: using phase-shift modulation control The sub-module SM of the secondary side MMC is soft charged.
上述多阶段软充控制方法应用于模块化多电平直流固态变压器，在不同阶段采用不同的软充电策略，实现了模块化多电平直流固态变压器子模块电容的的快速、稳定充电，减小了变压器启动时交流侧与直流侧的电流尖峰，保护了子模块中的功率器件和高频变压器，增加了电容的使用寿命，有力利于系统的安全运行。The above-mentioned multi-stage soft charging control method is applied to a modular multi-level DC solid-state transformer, and different soft charging strategies are adopted at different stages to realize the rapid and stable charging of the sub-module capacitance of the modular multi-level DC solid-state transformer, and reduce This reduces the current spikes on the AC side and the DC side when the transformer is started, protects the power devices and high-frequency transformers in the sub-modules, increases the service life of the capacitors, and greatly facilitates the safe operation of the system.
作为本发明技术方案的进一步改进，所述的子模块SM包含第一功率开关管(S 1)、第二功率开关管(S 2)、并联电容C、第一反并联二极管(VD 1)、第二反并联二极管(VD 2)；所述的第一功率开关管(S 1)、第二功率开关管(S 2)构成半桥结构；第一反并联二极管(VD 1)反并联在第一功率开关管(S 1)两端；第二反并联二极管(VD 2)反并联在第二功率开关管(S 2)两端；所述的并联电容C并联在所述的半桥结构的两端；所述的半桥结构的中点做为子模块SM的输入端。 As a further improvement of the technical solution of the present invention, the sub-module SM includes a first power switch tube (S 1 ), a second power switch tube (S 2 ), a parallel capacitor C, a first anti-parallel diode (VD 1 ), The second anti-parallel diode (VD 2 ); the first power switch tube (S 1 ) and the second power switch tube (S 2 ) form a half-bridge structure; the first anti-parallel diode (VD 1 ) is connected in anti-parallel Two ends of a power switch (S 1 ); a second anti-parallel diode (VD 2 ) is connected in anti-parallel to both ends of the second power switch (S 2 ); the parallel capacitor C is connected in parallel to the half-bridge structure Both ends; the midpoint of the half-bridge structure is used as the input end of the sub-module SM.
作为本发明技术方案的进一步改进，所述的子模块SM有两种工作状态：As a further improvement of the technical solution of the present invention, the sub-module SM has two working states:
a)闭锁状态：所述的子模块SM中的第一功率开关管(S 1)以及第二功率开关管(S 2)的驱动脉冲在整个开关周期都为0； a) Locked state: the driving pulses of the first power switch tube (S 1 ) and the second power switch tube (S 2 ) in the sub-module SM are all 0 during the entire switching period;
b)旁路状态：所述的子模块SM中的第一功率开关管(S 1)的驱动脉冲在整个开关周期都为0，第二功率开关管(S 2)的驱动脉冲是占空比为D的PWM信号波；所述的占空比D为一次侧桥臂电流平均值从周期初始值上升至给定一次侧桥臂电流峰值所需时间的占比。 b) Bypass state: the driving pulse of the first power switch tube (S 1 ) in the sub-module SM is 0 throughout the switching period, and the driving pulse of the second power switch tube (S 2 ) is the duty cycle Is the PWM signal wave of D; the duty ratio D is the proportion of the time required for the average value of the primary side bridge arm current to rise from the initial value of the cycle to the given peak value of the primary side bridge arm current.
作为本发明技术方案的进一步改进，所述的阶段一具体为：As a further improvement of the technical solution of the present invention, the first stage is specifically:
1)控制一次侧MMC与二次侧MMC的所有子模块SM都工作在闭锁状态；1) All sub-modules SM that control the primary side MMC and the secondary side MMC are working in a locked state;
2)打开限流开关(S d)，将限流电阻(R d)投切到电路中，一次侧所有子模块SM的并联电容C通过全波整流充电。 2) Turn on the current-limiting switch (S d ), switch the current-limiting resistor (R d ) into the circuit, and charge the parallel capacitors C of all sub-modules SM on the primary side through full-wave rectification.
3)并联电容C的电压充电至一次侧电容标称电压(V 1 *)的一半后，一次侧MMC的子模块不控充电阶段结束。 3) After the voltage of the parallel capacitor C is charged to half of the nominal voltage (V 1 * ) of the primary side capacitor, the uncontrolled charging phase of the sub-module of the primary side MMC ends.
作为本发明技术方案的进一步改进，所述的阶段二具体为：As a further improvement of the technical solution of the present invention, the second stage is specifically:
Ⅰ)闭合限流开关(S d)，将限流电阻(R d)旁路；二次侧MMC的所有子模块SM仍工作在闭锁状态； Ⅰ) Close the current-limiting switch (S d ), and bypass the current-limiting resistor (R d ); all sub-modules SM of the secondary side MMC are still working in a locked state;
Ⅱ)通过电流采样得到一次侧MMC的第一桥臂和第二桥臂的电流值i a、i b，计算桥臂电流平均值i 1；所述桥臂电流平均值的计算公式为: Ⅱ) Obtain the current values i a and i b of the first and second bridge arms of the primary side MMC through current sampling, and calculate the average value of the bridge arm current i 1 ; the calculation formula of the average value of the bridge arm current is:
i 1＝0.5(i a+i b) i 1 ＝0.5(i a +i b )
Ⅲ)比较桥臂电流平均值i 1与给定桥臂电流峰值i * peak的大小关系： Ⅲ) Compare the relationship between the average value of the bridge arm current i 1 and the given bridge arm current peak value i * peak:
若i 1﹤i * peak，控制一次侧MMC的所有子模块SM工作在旁路状态，桥臂的电流值上升； If i 1 <i * peak , control all sub-modules SM of the primary side MMC to work in the bypass state, and the current value of the bridge arm rises;
若i 1≥i * peak，控制一次侧MMC的所有子模块SM工作在闭锁状态，桥臂的电流流过第一反并联二极管(VD 1)对子模块SM的并联电容C充电。 If i 1 ≥ i * peak , all sub-modules SM controlling the primary side MMC work in a locked state, and the current of the bridge arm flows through the first anti-parallel diode (VD 1 ) to charge the parallel capacitor C of the sub-module SM.
Ⅳ)重复Ⅲ)，当子模块SM的并联电容C的电压充电至其标称电压时，一次侧子MMC的子模块可控充电阶段结束。Ⅳ) Repeat Ⅲ), when the voltage of the parallel capacitor C of the sub-module SM is charged to its nominal voltage, the controllable charging phase of the sub-module of the primary-side sub-MMC ends.
作为本发明技术方案的进一步改进，所述的阶段三具体为：As a further improvement of the technical solution of the present invention, the stage three is specifically as follows:
a)一次侧MMC的两桥臂所有子模块SM的第一功率开关管(S 1)在整个周期内关断，一次侧MMC的两桥臂所有子模块SM的第二功率开关管(S 2) 采用移相调制；二次侧MMC的所有子模块SM都工作在闭锁状态； a) The first power switch tube (S 1 ) of all sub-modules SM of the two bridge arms of the primary side MMC is turned off during the entire cycle, and the second power switch tube (S 2) of all the sub-modules SM of the two bridge arms of the primary side MMC ) Phase-shift modulation is adopted; all sub-modules SM of the secondary side MMC are working in a locked state;
b)控制一次侧MMC的两桥臂所有子模块SM的第二功率开关管(S 2)的移相角
Figure PCTCN2020134878-appb-000001
从0至π线性增大，则一次侧MMC向二次MMC传输的功率从0增加到最大，对应的一次侧MMC向二次MMC传输的功率可以从0到最大值范围内调节； b) Control the phase shift angle of the second power switch tube (S 2 ) of all sub-modules SM of the two bridge arms of the primary side MMC
Figure PCTCN2020134878-appb-000001
Linear increase from 0 to π, the power transmitted from the primary side MMC to the secondary MMC increases from 0 to the maximum, and the corresponding power transmitted from the primary side MMC to the secondary MMC can be adjusted from 0 to the maximum;
c)选择一次侧MMC向二次MMC传输的功率的大小，对二次侧子模块并联电容C进行充电；二次侧子模块并联电容C充电至二次侧电容标称电压(V 2 *)时结束充电。 c) Select the size of the power transferred from the primary side MMC to the secondary MMC, and charge the parallel capacitor C of the secondary side sub-module; charge the parallel capacitor C of the secondary side sub-module to the nominal voltage of the secondary side capacitor (V 2 * ) End charging at the time.
作为本发明技术方案的进一步改进，所述的一次侧电容标称电压(V 1 *)按照以下公式计算： As a further improvement of the technical solution of the present invention, the nominal voltage (V 1 * ) of the primary side capacitor is calculated according to the following formula:
Figure PCTCN2020134878-appb-000002
Figure PCTCN2020134878-appb-000002
其中，V 1 *一次侧电容标称电压；V dc1为输入源的电压，M为一次侧MMC每半桥臂子模块SM的个数。 Among them, V 1 * the nominal voltage of the primary side capacitor; V dc1 is the voltage of the input source, and M is the number of sub-modules SM per half bridge arm of the primary side MMC.
作为本发明技术方案的进一步改进，所述的二次侧电容标称电压(V 2 *)按照以下公式计算： As a further improvement of the technical solution of the present invention, the nominal voltage (V 2 * ) of the secondary side capacitor is calculated according to the following formula:
Figure PCTCN2020134878-appb-000003
Figure PCTCN2020134878-appb-000003
其中，V 2 *一次侧电容标称电压；V dc2为输出源的电压，N为二次侧MMC每半桥臂子模块SM的个数。 Among them, V 2 * the nominal voltage of the primary side capacitor; V dc2 is the voltage of the output source, and N is the number of sub-modules SM per half bridge arm of the secondary side MMC.
一种多电平直流固态变压器多阶段软充控制系统，所述的模块化多电平直流固态变压器，包括输入源V dc1，输出源V dc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧 MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源V dc1连接；所述的输入源V dc1为直流源；输入源V dc1给一次侧MMC供电；所述的输出源V dc2为直流源或负载连接在二次侧MMC的输出端； A multi-stage soft charging control system for a multi-level DC solid-state transformer. The modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, a secondary side MMC, and a current-limiting resistor R d , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the secondary MMC-side sub-module SM comprises a plurality of H-bridge circuit configuration; the primary side and the secondary side MMC MMC connected by high-frequency transformer T; after the current limiting resistor R d and S d limiting switch in parallel with the first end The other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source or the load is connected to the secondary The output terminal of the side MMC;
所述的多阶段软充控制系统包括：模块一，一次侧MMC的子模块SM不控充电模块；模块二：使用峰值电流控制一次侧MMC的子模块SM软充电模块；模块三：使用移相调制控制二次侧MMC的子模块SM软充电模块。The multi-stage soft charging control system includes: module one, the sub-module SM of the primary side MMC does not control the charging module; module two: using the peak current to control the sub-module SM soft charging module of the primary side MMC; module three: using phase shifting Modulate and control the sub-module SM soft charging module of the secondary side MMC.
作为本发明技术方案的进一步改进，所述的一次侧MMC还包含第一桥臂和第二桥臂；所述的一次侧MMC的第一桥臂和第二桥臂构成H桥结构；As a further improvement of the technical solution of the present invention, the primary side MMC further includes a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm of the primary side MMC constitute an H bridge structure;
所述的一次侧MMC的第一桥臂包含上半桥臂和下半桥臂；所述的一次侧MMC的第二桥臂也包含上半桥臂和下半桥臂；The first bridge arm of the primary side MMC includes an upper half bridge arm and a lower half bridge arm; the second bridge arm of the primary side MMC also includes an upper half bridge arm and a lower half bridge arm;
所述的一次侧MMC的第一桥臂的上半桥臂包含M个子模块SM以及一个第一桥臂上电感L a1，所述的M个子模块SM以及一个第一桥臂上电感L a1依次串联；所述的一次侧MMC的第一桥臂的下半桥臂包含M个子模块SM以及一个第一桥臂下电感L a2，所述的一次侧MMC的第一桥臂的下半桥臂的结构与所述的一次侧MMC的第一桥臂的上半桥臂的结构对称；对称点为a点； The upper half of the first bridge arm of the primary side MMC includes M sub-modules SM and an inductance La1 on the first bridge arm, and the M sub-modules SM and an inductance La1 on the first bridge arm are in turn series; lower half bridge arm of the first arm of the primary side of the MMC comprises M sub-module SM and the inductor L a2 next first bridge arm, the first arm of a half bridge arm lower side of the MMC The structure of is symmetrical with the structure of the upper half of the first bridge arm of the primary side MMC; the symmetry point is point a;
所述的一次侧MMC的第二桥臂的上半桥臂包含M个子模块SM以及一个第二桥臂上电感L b1，所述的M个子模块SM以及一个第二桥臂上电感L b1依次串联；所述的一次侧MMC的第二桥臂的下半桥臂包含M个子模块SM以及一个第二桥臂下电感L b2，所述的一次侧MMC的第二桥臂的下半桥臂的结构与所述的一次侧MMC的第二桥臂的上半桥臂的结构对称；对称点为b点； The upper half of the second bridge arm of the primary side MMC includes M sub-modules SM and an inductance L b1 on the second bridge arm. The M sub-modules SM and the inductance L b1 on the second bridge arm are in turn In series; the lower half of the second leg of the primary side MMC includes M submodules SM and a second lower inductance L b2 , the lower half of the second leg of the primary side MMC The structure of is symmetrical with the structure of the upper half of the second bridge arm of the primary side MMC; the symmetry point is point b;
所述的二次侧MMC包含第三桥臂和第四桥臂；所述的二次侧MMC的第三桥臂和第四桥臂构成H桥结构；The secondary side MMC includes a third bridge arm and a fourth bridge arm; the third bridge arm and the fourth bridge arm of the secondary side MMC constitute an H bridge structure;
所述的二次侧MMC的第三桥臂包含上半桥臂和下半桥臂；所述的二次侧MMC的第四桥臂也包含上半桥臂和下半桥臂；The third bridge arm of the secondary side MMC includes an upper half bridge arm and a lower half bridge arm; the fourth bridge arm of the secondary side MMC also includes an upper half bridge arm and a lower half bridge arm;
所述的二次侧MMC的第三桥臂的上半桥臂包含N个子模块SM以及一个第三桥臂上电感L c1，所述的N个子模块SM以及一个第三桥臂上电感L c1依次串联；所述的二次侧MMC的第三桥臂的下半桥臂包含N个子模块SM以及一个第三桥臂下电感L c2，所述的二次侧MMC的第三桥臂的下半桥臂的结构与所述的二次侧MMC的第三桥臂的上半桥臂的结构对称；对称点为c点； The upper half of the third bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L c1 on the third bridge arm, the N sub-modules SM and an inductance L c1 on the third bridge arm In series; the lower half of the third bridge arm of the secondary side MMC includes N sub-modules SM and a lower inductance L c2 of the third bridge arm, and the lower half of the third bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the third bridge arm of the secondary side MMC; the symmetry point is point c;
所述的二次侧MMC的第四桥臂的上半桥臂包含N个子模块SM以及一个第四桥臂上电感L d1，所述的N个子模块SM以及一个第四桥臂上电感L d1依次串联；所述的二次侧MMC的第四桥臂的下半桥臂包含N个子模块SM以及一个第四桥臂下电感L d2，所述的二次侧MMC的第四桥臂的下半桥臂的结构与所述的二次侧MMC的第四桥臂的上半桥臂的结构对称；对称点为d点； The upper half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L d1 on the fourth bridge arm, the N sub-modules SM and an inductance L d1 on the fourth bridge arm In series; the lower half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and a fourth bridge arm lower inductance L d2 , the lower half of the fourth bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the fourth bridge arm of the secondary side MMC; the symmetry point is point d;
所述的高频变压器T的四个端子分别与a点、b点、c点、d点连接。The four terminals of the high-frequency transformer T are respectively connected to point a, point b, point c, and point d.
本发明的优点在于：The advantages of the present invention are:
(1)本发明的多阶段软充控制方法应用于模块化多电平直流固态变压器，在不同阶段采用不同的软充电策略，实现了模块化多电平直流固态变压器子模块电容的的快速、稳定充电，减小了变压器启动时交流侧与直流侧的电流尖峰，保护了子模块中的功率器件和高频变压器，增加了电容的使用寿命，有力利于系统的安全运行。(1) The multi-stage soft charging control method of the present invention is applied to a modular multi-level DC solid-state transformer, and different soft charging strategies are adopted at different stages to realize the rapid, rapid, and rapid, Stable charging reduces the current spikes on the AC side and DC side when the transformer is started, protects the power devices and high-frequency transformers in the sub-modules, increases the service life of the capacitors, and greatly benefits the safe operation of the system.
(2)本发明的多阶段软充控制方法采用的软充电策略控制原理清晰， 外围控制电路结构简单，易于实现。(2) The soft charging strategy control principle adopted by the multi-stage soft charging control method of the present invention is clear, and the peripheral control circuit has a simple structure and is easy to implement.
附图说明Description of the drawings
图1是本发明实施例模块化多电平直流固态变压器拓扑图。Fig. 1 is a topology diagram of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
图2是本发明实施例模块化多电平直流固态变压器多阶段软充控制方法的原理图。Fig. 2 is a schematic diagram of a multi-stage soft charging control method of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
图3是本发明实施例模块化多电平直流固态变压器多阶段软充控制方法的流程图。Fig. 3 is a flowchart of a multi-stage soft charging control method of a modular multi-level DC solid-state transformer according to an embodiment of the present invention.
图4是本发明实施例模块化多电平直流固态变压器子模块的结构图。Fig. 4 is a structural diagram of a modular multi-level DC solid-state transformer sub-module according to an embodiment of the present invention.
图5是本发明实施例模块化多电平直流固态变压器子模块的工作在闭锁状态时的驱动波形图。Fig. 5 is a driving waveform diagram of a modular multi-level direct current solid-state transformer sub-module working in a locked state according to an embodiment of the present invention.
图6是本发明实施例模块化多电平直流固态变压器子模块的工作在旁路状态时的驱动波形图。Fig. 6 is a driving waveform diagram of a modular multi-level direct current solid-state transformer sub-module working in a bypass state according to an embodiment of the present invention.
图7是本发明实施例M＝1，N＝1时模块化多电平直流固态变压器拓扑图。Fig. 7 is a topology diagram of a modular multi-level direct current solid-state transformer when M=1 and N=1 in an embodiment of the present invention.
图8是本发明实施例M＝1，N＝1时模块化多电平直流固态变压器一次侧MMC两桥臂间的移相角为0时的驱动波形图；8 is a driving waveform diagram when the phase shift angle between the two bridge arms of the primary side MMC of the modular multilevel DC solid-state transformer is 0 when M=1 and N=1 in the embodiment of the present invention;
图9是本发明实施例M＝1，N＝1时模块化多电平直流固态变压器一次侧MMC两桥臂间的移相角为π时的驱动波形图。Fig. 9 is a driving waveform diagram when the phase shift angle between the two bridge arms of the primary side MMC of the modular multilevel DC solid-state transformer is π when M=1 and N=1 in the embodiment of the present invention.
具体实施方式Detailed ways
为使本发明实施例的目的、技术方案和优点更加清楚，下面将结合本发明实施例，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发 明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. Examples, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
下面结合说明书附图以及具体的实施例对本发明的技术方案作进一步描述：The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments of the specification:
实施例一Example one
如图1所示，一种多电平直流固态变压器多阶段软充控制方法，所述的模块化多电平直流固态变压器，包括输入源V dc1，输出源V dc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源V dc1连接；所述的输入源V dc1为直流源；输入源V dc1给一次侧MMC供电；所述的输出源V dc2为直流源或负载连接在二次侧MMC的输出端。 As shown in Figure 1, a multi-stage soft charging control method for a multi-level DC solid-state transformer. The modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC. Side MMC, current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes multiple sub-modules SM to form an H-bridge circuit The secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd and the current-limiting switch S d After parallel connection, one end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source Or the load is connected to the output end of the secondary side MMC.
如图2和图3所示，所述的多阶段软充控制方法包括：阶段一，一次侧MMC的子模块SM不控充电；阶段二：使用峰值电流控制一次侧MMC的子模块SM软充电；阶段三：使用移相调制控制二次侧MMC的子模块SM软充电。As shown in Figures 2 and 3, the described multi-stage soft charging control method includes: stage one, the sub-module SM of the primary side MMC does not control charging; stage two: using the peak current to control the sub-module SM of the primary side MMC soft charging ; Phase 3: Use phase-shift modulation to control the soft charging of the sub-module SM of the secondary side MMC.
如图4所示，所述的子模块SM包含第一功率开关管S 1、第二功率开关管S 2、并联电容C、第一反并联二极管VD 1、第二反并联二极管VD 2；所述的第一功率开关管S 1、第二功率开关管S 2构成半桥结构；第一反并联二极管VD 1反并联在第一功率开关管S 1两端；第二反并联二极管VD 2反并联在第二功率开关管S 2两端；所述的并联电容C并联在所述的半桥结构的两端；所 述的半桥结构的中点做为子模块SM的输入端。 As shown in Figure 4, the sub-module SM includes a first power switch S 1 , a second power switch S 2 , a parallel capacitor C, a first anti-parallel diode VD 1 , and a second anti-parallel diode VD 2 ; The first power switch tube S 1 and the second power switch tube S 2 described above constitute a half-bridge structure; the first anti-parallel diode VD 1 is connected in anti-parallel to both ends of the first power switch tube S 1 ; the second anti-parallel diode VD 2 is anti-parallel connected in parallel across the second power switch S 2; ends of the parallel capacitor C connected in parallel with the half-bridge; the midpoint of the half-bridge configuration as the input terminal of the SM module.
如图5和图6所示，所述的子模块SM有两种工作状态：As shown in Figure 5 and Figure 6, the sub-module SM has two working states:
a)闭锁状态：所述的子模块SM中的第一功率开关管S 1以及第二功率开关管S 2的驱动脉冲在整个开关周期都为0； a) Locked state: the driving pulses of the first power switch tube S 1 and the second power switch tube S 2 in the sub-module SM are all 0 during the entire switching period;
b)旁路状态：所述的子模块SM中的第一功率开关管S 1的驱动脉冲在整个开关周期都为0，第二功率开关管S 2的驱动脉冲是占空比为D的PWM信号波；所述的占空比D为一次侧桥臂电流平均值从周期初始值上升至给定一次侧桥臂电流峰值所需时间的占比。 b) Bypass state: the driving pulse of the first power switch S 1 in the sub-module SM is 0 during the entire switching period, and the driving pulse of the second power switch S 2 is a PWM with a duty cycle of D Signal wave; the duty cycle D is the ratio of the time required for the average value of the primary side bridge arm current to rise from the initial value of the cycle to the given peak value of the primary side bridge arm current.
所述的阶段一具体为：The first stage is specifically:
1)控制一次侧MMC与二次侧MMC的所有子模块SM都工作在闭锁状态；1) All sub-modules SM that control the primary side MMC and the secondary side MMC are working in a locked state;
2)打开限流开关S d，将限流电阻R d投切到电路中，一次侧所有子模块SM的并联电容C通过全波整流充电。 2) Open the current-limiting switch S d , switch the current-limiting resistor Rd into the circuit, and charge the parallel capacitors C of all sub-modules SM on the primary side through full-wave rectification.
如图7所示，取M＝1，N＝1时，所述的全波整流充电电流的路径为：As shown in Figure 7, when M=1 and N=1, the path of the full-wave rectified charging current is:
一次侧MMC的第一桥臂充电电流的路径为：V dc1正极→R d→VD11→C11→L a1→L a2→VD13→C13→V dc1负极； The path of the charging current of the first leg of the primary side MMC is: V dc1 positive→R d →VD11→C11→L a1 →L a2 →VD13→C13→V dc1 negative;
一次侧MMC的第二桥臂充电电流的路径为：V dc1正极→R d→VD21→C12→L b1→L b2→VD23→C14→V dc1负极。 The path of the charging current of the second leg of the primary side MMC is: V dc1 positive→R d →VD21→C12→L b1 →L b2 →VD23→C14→V dc1 negative.
3)并联电容C的电压充电至一次侧电容标称电压V 1 *的一半后，一次侧MMC的子模块不控充电阶段结束。 3) After the voltage of the parallel capacitor C is charged to half of the nominal voltage V 1 * of the primary side capacitor, the uncontrolled charging phase of the sub-module of the primary side MMC ends.
所述的一次侧电容标称电压V 1 *按照以下公式计算： The nominal voltage V 1 * of the primary side capacitor is calculated according to the following formula:
Figure PCTCN2020134878-appb-000004
Figure PCTCN2020134878-appb-000004
其中，V 1 *一次侧电容标称电压；V dc1为输入源的电压，M为一次侧MMC 每半桥臂子模块SM的个数。 Among them, V 1 * the nominal voltage of the primary-side capacitor; V dc1 is the voltage of the input source, and M is the number of sub-modules SM per half-bridge arm of the primary-side MMC.
所述的阶段二具体为：The second stage is specifically:
Ⅰ)闭合限流开关S d，将限流电阻R d旁路；二次侧MMC的所有子模块SM仍工作在闭锁状态； Ⅰ) Close the current-limiting switch S d and bypass the current-limiting resistor Rd ; all sub-modules SM of the secondary side MMC are still working in the locked state;
Ⅱ)通过电流采样得到一次侧MMC的第一桥臂和第二桥臂的电流值i a、i b，计算桥臂电流平均值i 1；所述桥臂电流平均值的计算公式为: Ⅱ) Obtain the current values i a and i b of the first and second bridge arms of the primary side MMC through current sampling, and calculate the average value of the bridge arm current i 1 ; the calculation formula of the average value of the bridge arm current is:
i 1＝0.5(i a+i b) i 1 ＝0.5(i a +i b )
Ⅲ)比较桥臂电流平均值i 1与给定桥臂电流峰值i * peak的大小关系： Ⅲ) Compare the relationship between the average value of the bridge arm current i 1 and the given bridge arm current peak value i * peak:
若i 1﹤i * peak，控制一次侧MMC的所有子模块SM工作在旁路状态，桥臂的电流值上升； If i 1 <i * peak , control all sub-modules SM of the primary side MMC to work in the bypass state, and the current value of the bridge arm rises;
若i 1≥i * peak，控制一次侧MMC的所有子模块SM工作在闭锁状态，桥臂的电流流过第一反并联二极管VD 1对子模块SM的并联电容C充电。 If i 1 ≥ i * peak , all sub-modules SM controlling the primary side MMC work in a locked state, and the current of the bridge arm flows through the first anti-parallel diode VD 1 to charge the parallel capacitor C of the sub-module SM.
Ⅳ)重复Ⅲ)，当子模块SM的并联电容C的电压充电至其标称电压时，一次侧子MMC的子模块可控充电阶段结束。Ⅳ) Repeat Ⅲ), when the voltage of the parallel capacitor C of the sub-module SM is charged to its nominal voltage, the controllable charging phase of the sub-module of the primary-side sub-MMC ends.
所述的阶段三具体为：The stage three is specifically:
a)一次侧MMC的两桥臂所有子模块SM的第一功率开关管S 1在整个周期内关断，一次侧MMC的两桥臂所有子模块SM的第二功率开关管S 2采用移相调制；二次侧MMC的所有子模块SM都工作在闭锁状态； a) The first power switching tube S 1 of all sub-modules SM of the two bridge arms of the primary side MMC is turned off during the entire cycle, and the second power switching tube S 2 of all the sub-modules SM of the two bridge arms of the primary side MMC adopts phase shifting. Modulation; all sub-modules SM of the secondary side MMC are working in a locked state;
b)控制一次侧MMC的两桥臂所有子模块SM的第二功率开关管S 2的移相角
Figure PCTCN2020134878-appb-000005
从0至π线性增大，则一次侧MMC向二次MMC传输的功率从0增加到最大，对应的一次侧MMC向二次MMC传输的功率可以从0到最大值范围内调节； b) Control the phase shift angle of the second power switch S 2 of all sub-modules SM of the two bridge arms of the primary side MMC
Figure PCTCN2020134878-appb-000005
Linear increase from 0 to π, the power transmitted from the primary side MMC to the secondary MMC increases from 0 to the maximum, and the corresponding power transmitted from the primary side MMC to the secondary MMC can be adjusted from 0 to the maximum;
c)选择一次侧MMC向二次MMC传输的功率的大小，对二次侧子模块并联电容C进行充电；二次侧子模块并联电容C充电至二次侧电容标称电压V 2 *时结束充电。 c) Select the size of the power transmitted from the primary side MMC to the secondary MMC, and charge the secondary side sub-module parallel capacitor C; the secondary side sub-module parallel capacitor C is charged to the nominal voltage of the secondary side capacitor V 2 * . Charge.
所述的二次侧电容标称电压V 2 *按照以下公式计算： The nominal voltage V 2 * of the secondary side capacitor is calculated according to the following formula:
Figure PCTCN2020134878-appb-000006
Figure PCTCN2020134878-appb-000006
其中，V 2 *一次侧电容标称电压；V dc2为输出源的电压，N为二次侧MMC每半桥臂子模块SM的个数。 Among them, V 2 * the nominal voltage of the primary side capacitor; V dc2 is the voltage of the output source, and N is the number of sub-modules SM per half bridge arm of the secondary side MMC.
结合图7、图8和图9对移相调制进行说明，此时取M＝1，N＝1。The phase shift modulation will be described with reference to FIG. 7, FIG. 8, and FIG. 9. At this time, M=1 and N=1.
(1)移相角
Figure PCTCN2020134878-appb-000007
为0时的开关管的波形，此时，一次侧MMC的电流通过二极管续流； (1) Phase shift angle
Figure PCTCN2020134878-appb-000007
The waveform of the switch tube when it is 0. At this time, the current of the primary side MMC flows through the diode;
一次侧MMC电流的续流路径为：S12→L a1→L s→L b1→VD22→S12；此时，一次侧MMC向二次MMC传输的功率为0。 The freewheeling path of the primary side MMC current is: S12→L a1 →L s →L b1 →VD22→S12; at this time, the power transmitted from the primary side MMC to the secondary MMC is zero.
(2)移相角
Figure PCTCN2020134878-appb-000008
为π时的开关管的波形，此时一次侧MMC的通过高频变压器T向二次MMC传输的功率为最大功率；此时， (2) Phase shift angle
Figure PCTCN2020134878-appb-000008
Is the waveform of the switch tube when π, at this time, the power transmitted from the primary side MMC to the secondary MMC through the high-frequency transformer T is the maximum power; at this time,
在开关管的波形正半周，一次侧MMC电流流通路径为：V dc1正极→S12→L a1→L s→L b2→S24→V dc1负极； In the positive half-cycle of the switching tube's waveform, the primary-side MMC current flow path is: V dc1 positive→S12→L a1 →L s →L b2 →S24→V dc1 negative;
在开关管的波形负半周，一次侧MMC电流流通路径为：V dc1正极→S22→L b1→L s→L a2→S14→V dc1负极。 In the negative half cycle of the waveform of the switching tube, the primary side MMC current flow path is: V dc1 positive → S22 → L b1 → L s → La2 → S14 → V dc1 negative.
结合图7、图8和图9对二次侧子模块并联电容充电进行说明，此时取M＝1，N＝1。The charging of the parallel capacitors of the secondary side sub-modules will be described with reference to Figs. 7, 8, and 9, at this time, M=1 and N=1.
当一次侧MMC向二次MMC传输的功率不为0时，二次侧子模块并联电容立即充电，充电电流的路径为：When the power transmitted from the primary side MMC to the secondary MMC is not 0, the parallel capacitors of the secondary side sub-modules are immediately charged, and the path of the charging current is:
在开关管的波形正半周，二次侧子模块充电电流的路径分为两路，同时对电容C22和电容C23进行充电；对电容C22进行充电的路径为：c点→L c1→VD32→VD41→C22→L d1→d点；对电容C23进行充电的路径为：c点→L c2→VD33→C23→VD44→L d2→d点； In the positive half cycle of the switching tube, the charging current path of the secondary side sub-module is divided into two paths, and the capacitor C22 and the capacitor C23 are charged at the same time; the path for charging the capacitor C22 is: point c→L c1 →VD32→VD41 → C22 → L d1 → point d; the path to charge the capacitor C23 is: point c → L c2 → VD33 → C23 → VD44 → L d2 → point d;
在开关管的波形负半周，二次侧子模块充电电流的路径分为两路，同时对电容C21和电容C24进行充电；对电容C21进行充电的路径为：d点→L d1→VD42→VD31→C21→L c1→c点；对电容C24进行充电的路径为：d点→L d2→VD43→C24→VD34→L c2→c点。 In the negative half cycle of the waveform of the switch tube, the charging current path of the secondary side sub-module is divided into two paths, and the capacitor C21 and the capacitor C24 are charged at the same time; the path for charging the capacitor C21 is: point d→L d1 →VD42→VD31 → C21 → L c1 → point c; the path to charge the capacitor C24 is: point d → L d2 → VD43 → C24 → VD34 → L c2 → point c.
实施例二Example two
如图1所示，一种多电平直流固态变压器多阶段软充控制系统，所述的模块化多电平直流固态变压器，包括输入源V dc1，输出源V dc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源V dc1连接；所述的输入源V dc1为直流源；输入源V dc1给一次侧MMC供电；所述的输出源V dc2为直流源或负载连接在二次侧MMC的输出端。 As shown in Figure 1, a multi-stage soft charging control system for a multi-level DC solid-state transformer. The modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC. Side MMC, current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes multiple sub-modules SM to form an H-bridge circuit The secondary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; the primary-side MMC and the secondary-side MMC are connected through a high-frequency transformer T; the current-limiting resistor Rd and the current-limiting switch S d After parallel connection, one end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source Or the load is connected to the output end of the secondary side MMC.
所述的多阶段软充控制系统包括：模块一，一次侧MMC的子模块SM不控充电模块；模块二：使用峰值电流控制一次侧MMC的子模块SM软充电模块；模块三：使用移相调制控制二次侧MMC的子模块SM软充电模块。The multi-stage soft charging control system includes: module one, the sub-module SM of the primary side MMC does not control the charging module; module two: using the peak current to control the sub-module SM soft charging module of the primary side MMC; module three: using phase shifting Modulate and control the sub-module SM soft charging module of the secondary side MMC.
所述的一次侧MMC还包含第一桥臂和第二桥臂；所述的一次侧MMC的第 一桥臂和第二桥臂构成H桥结构。The primary side MMC further includes a first bridge arm and a second bridge arm; the first bridge arm and the second bridge arm of the primary side MMC constitute an H bridge structure.
所述的一次侧MMC的第一桥臂包含上半桥臂和下半桥臂；所述的一次侧MMC的第二桥臂也包含上半桥臂和下半桥臂。The first bridge arm of the primary side MMC includes an upper half bridge arm and a lower half bridge arm; the second bridge arm of the primary side MMC also includes an upper half bridge arm and a lower half bridge arm.
所述的一次侧MMC的第一桥臂的上半桥臂包含M个子模块SM以及一个第一桥臂上电感L a1，所述的M个子模块SM以及一个第一桥臂上电感L a1依次串联；所述的一次侧MMC的第一桥臂的下半桥臂包含M个子模块SM以及一个第一桥臂下电感L a2，所述的一次侧MMC的第一桥臂的下半桥臂的结构与所述的一次侧MMC的第一桥臂的上半桥臂的结构对称；对称点为a点。 The upper half of the first bridge arm of the primary side MMC includes M sub-modules SM and an inductance La1 on the first bridge arm, and the M sub-modules SM and an inductance La1 on the first bridge arm are in turn series; lower half bridge arm of the first arm of the primary side of the MMC comprises M sub-module SM and the inductor L a2 next first bridge arm, the first arm of a half bridge arm lower side of the MMC The structure of is symmetrical with the structure of the upper half of the first bridge arm of the primary side MMC; the symmetry point is point a.
所述的一次侧MMC的第二桥臂的上半桥臂包含M个子模块SM以及一个第二桥臂上电感L b1，所述的M个子模块SM以及一个第二桥臂上电感L b1依次串联；所述的一次侧MMC的第二桥臂的下半桥臂包含M个子模块SM以及一个第二桥臂下电感L b2，所述的一次侧MMC的第二桥臂的下半桥臂的结构与所述的一次侧MMC的第二桥臂的上半桥臂的结构对称；对称点为b点。 The upper half of the second bridge arm of the primary side MMC includes M sub-modules SM and an inductance L b1 on the second bridge arm. The M sub-modules SM and the inductance L b1 on the second bridge arm are in turn In series; the lower half of the second leg of the primary side MMC includes M submodules SM and a second lower inductance L b2 , the lower half of the second leg of the primary side MMC The structure of is symmetrical with the structure of the upper half of the second bridge arm of the primary side MMC; the symmetry point is point b.
所述的二次侧MMC包含第三桥臂和第四桥臂；所述的二次侧MMC的第三桥臂和第四桥臂构成H桥结构。The secondary side MMC includes a third bridge arm and a fourth bridge arm; the third bridge arm and the fourth bridge arm of the secondary side MMC constitute an H bridge structure.
所述的二次侧MMC的第三桥臂包含上半桥臂和下半桥臂；所述的二次侧MMC的第四桥臂也包含上半桥臂和下半桥臂。The third bridge arm of the secondary side MMC includes an upper half bridge arm and a lower half bridge arm; the fourth bridge arm of the secondary side MMC also includes an upper half bridge arm and a lower half bridge arm.
所述的二次侧MMC的第三桥臂的上半桥臂包含N个子模块SM以及一个第三桥臂上电感L c1，所述的N个子模块SM以及一个第三桥臂上电感L c1依次串联；所述的二次侧MMC的第三桥臂的下半桥臂包含N个子模块SM以及一个第三桥臂下电感L c2，所述的二次侧MMC的第三桥臂的下半桥臂的结构与所述的二次侧MMC的第三桥臂的上半桥臂的结构对称；对称点为c点。 The upper half of the third bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L c1 on the third bridge arm, the N sub-modules SM and an inductance L c1 on the third bridge arm In series; the lower half of the third bridge arm of the secondary side MMC includes N sub-modules SM and a lower inductance L c2 of the third bridge arm, and the lower half of the third bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the third bridge arm of the secondary side MMC; the symmetry point is point c.
所述的二次侧MMC的第四桥臂的上半桥臂包含N个子模块SM以及一个第四桥臂上电感L d1，所述的N个子模块SM以及一个第四桥臂上电感L d1依次串联；所述的二次侧MMC的第四桥臂的下半桥臂包含N个子模块SM以及一个第四桥臂下电感L d2，所述的二次侧MMC的第四桥臂的下半桥臂的结构与所述的二次侧MMC的第四桥臂的上半桥臂的结构对称；对称点为d点。 The upper half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L d1 on the fourth bridge arm, the N sub-modules SM and an inductance L d1 on the fourth bridge arm In series; the lower half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and a fourth bridge arm lower inductance L d2 , the lower half of the fourth bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the fourth bridge arm of the secondary side MMC; the symmetry point is point d.
所述的高频变压器T的四个端子分别与a点、b点、c点、d点连接。The four terminals of the high-frequency transformer T are respectively connected to point a, point b, point c, and point d.
以上实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的精神和范围。The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, a person of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some of the technical features are equivalently replaced; these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

  1. 一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的模块化多电平直流固态变压器，包括输入源V dc1，输出源V dc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源V dc1连接；所述的输入源V dc1为直流源；输入源V dc1给一次侧MMC供电；所述的输出源V dc2为直流源或负载连接在二次侧MMC的输出端； A multi-stage soft charging control method for a multi-level DC solid-state transformer is characterized in that the modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC , Current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; MMC said secondary side comprises a plurality of sub-modules constituting the H bridge circuit SM; the primary side and the secondary side MMC MMC connected by high-frequency transformer T; the current limiting resistor R d d in parallel with the current limiting switch S The rear end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source or load Connect to the output terminal of the secondary side MMC;
    所述的多阶段软充控制方法包括：阶段一，一次侧MMC的子模块SM不控充电；阶段二：使用峰值电流控制一次侧MMC的子模块SM软充电；阶段三：使用移相调制控制二次侧MMC的子模块SM软充电。The multi-stage soft charging control method includes: stage one, the sub-module SM of the primary side MMC does not control charging; stage two: using the peak current to control the soft charging of the sub-module SM of the primary side MMC; stage three: using phase-shift modulation control The sub-module SM of the secondary side MMC is soft charged.
  2. 根据权利要求1所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的子模块SM包含第一功率开关管S 1、第二功率开关管S 2、并联电容C、第一反并联二极管VD 1、第二反并联二极管VD 2；所述的第一功率开关管S 1、第二功率开关管S 2构成半桥结构；第一反并联二极管VD 1反并联在第一功率开关管S 1两端；第二反并联二极管VD 2反并联在第二功率开关管S 2两端；所述的并联电容C并联在所述的半桥结构的两端；所述的半桥结构的中点做为子模块SM的输入端。 The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 1, wherein the sub-module SM includes a first power switch S 1 , a second power switch S 2 , and a parallel connection The capacitor C, the first anti-parallel diode VD 1 , and the second anti-parallel diode VD 2 ; the first power switch S 1 and the second power switch S 2 constitute a half-bridge structure; the first anti-parallel diode VD 1 is reversed Connected in parallel at both ends of the first power switch S 1 ; a second anti-parallel diode VD 2 is connected in anti-parallel at both ends of the second power switch S 2 ; the parallel capacitor C is connected in parallel at both ends of the half-bridge structure; The midpoint of the half-bridge structure is used as the input terminal of the sub-module SM.
  3. 根据权利要求2所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的子模块SM有两种工作状态：The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 2, wherein the sub-module SM has two working states:
    a)闭锁状态：所述的子模块SM中的第一功率开关管S 1以及第二功率开 关管S 2的驱动脉冲在整个开关周期都为0； a) Locked state: the driving pulses of the first power switch tube S 1 and the second power switch tube S 2 in the sub-module SM are all 0 during the entire switching period;
    b)旁路状态：所述的子模块SM中的第一功率开关管S 1的驱动脉冲在整个开关周期都为0，第二功率开关管S 2的驱动脉冲是占空比为D的PWM信号波；所述的占空比D为一次侧桥臂电流平均值从周期初始值上升至给定一次侧桥臂电流峰值所需时间的占比。 b) Bypass state: the driving pulse of the first power switch S 1 in the sub-module SM is 0 during the entire switching period, and the driving pulse of the second power switch S 2 is a PWM with a duty cycle of D Signal wave; the duty cycle D is the ratio of the time required for the average value of the primary side bridge arm current to rise from the initial value of the cycle to the given peak value of the primary side bridge arm current.
  4. 根据权利要求1所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的阶段一具体为：The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 1, wherein the first stage is specifically:
    1)控制一次侧MMC与二次侧MMC的所有子模块SM都工作在闭锁状态；1) All sub-modules SM that control the primary side MMC and the secondary side MMC are working in a locked state;
    2)打开限流开关S d，将限流电阻R d投切到电路中，一次侧所有子模块SM的并联电容C通过全波整流充电； 2) Open the current-limiting switch S d , switch the current-limiting resistor Rd into the circuit, and charge the parallel capacitors C of all sub-modules SM on the primary side through full-wave rectification;
    3)并联电容C的电压充电至一次侧电容标称电压V 1 *的一半后，一次侧MMC的子模块不控充电阶段结束。 3) After the voltage of the parallel capacitor C is charged to half of the nominal voltage V 1 * of the primary side capacitor, the uncontrolled charging phase of the sub-module of the primary side MMC ends.
  5. 根据权利要求1所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的阶段二具体为：The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 1, wherein the second stage is specifically:
    Ⅰ)闭合限流开关S d，将限流电阻R d旁路；二次侧MMC的所有子模块SM仍工作在闭锁状态； Ⅰ) Close the current-limiting switch S d and bypass the current-limiting resistor Rd ; all sub-modules SM of the secondary side MMC are still working in the locked state;
    Ⅱ)通过电流采样得到一次侧MMC的第一桥臂和第二桥臂的电流值i a、i b，计算桥臂电流平均值i 1；所述桥臂电流平均值的计算公式为: Ⅱ) Obtain the current values i a and i b of the first and second bridge arms of the primary side MMC through current sampling, and calculate the average value of the bridge arm current i 1 ; the calculation formula of the average value of the bridge arm current is:
    i 1＝0.5(i a+i b) i 1 ＝0.5(i a +i b )
    Ⅲ)比较桥臂电流平均值i 1与给定桥臂电流峰值i * peak的大小关系： Ⅲ) Compare the relationship between the average value of the bridge arm current i 1 and the given bridge arm current peak value i * peak:
    若i 1﹤i * peak，控制一次侧MMC的所有子模块SM工作在旁路状态，桥臂的电流值上升； If i 1 <i * peak , control all sub-modules SM of the primary side MMC to work in the bypass state, and the current value of the bridge arm rises;
    若i 1≥i * peak，控制一次侧MMC的所有子模块SM工作在闭锁状态，桥臂的电流流过第一反并联二极管(VD 1)对子模块SM的并联电容C充电； If i 1 ≥ i * peak , control all sub-modules SM of the primary side MMC to work in a locked state, and the current of the bridge arm flows through the first anti-parallel diode (VD 1 ) to charge the parallel capacitor C of the sub-module SM;
    Ⅳ)重复Ⅲ)，当子模块SM的并联电容C的电压充电至其标称电压时，一次侧子MMC的子模块可控充电阶段结束。Ⅳ) Repeat Ⅲ), when the voltage of the parallel capacitor C of the sub-module SM is charged to its nominal voltage, the controllable charging phase of the sub-module of the primary-side sub-MMC ends.
  6. 根据权利要求1所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的阶段三具体为：The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 1, wherein the third stage is specifically:
    a)一次侧MMC的两桥臂所有子模块SM的第一功率开关管S 1在整个周期内关断，一次侧MMC的两桥臂所有子模块SM的第二功率开关管S 2采用移相调制；二次侧MMC的所有子模块SM都工作在闭锁状态； a) The first power switching tube S 1 of all sub-modules SM of the two bridge arms of the primary side MMC is turned off during the entire cycle, and the second power switching tube S 2 of all the sub-modules SM of the two bridge arms of the primary side MMC adopts phase shifting. Modulation; all sub-modules SM of the secondary side MMC are working in a locked state;
    b)控制一次侧MMC的两桥臂所有子模块SM的第二功率开关管S 2的移相角
    Figure PCTCN2020134878-appb-100001
    从0至π线性增大，则一次侧MMC向二次MMC传输的功率从0增加到最大，对应的一次侧MMC向二次MMC传输的功率可以从0到最大值范围内调节；     b) Control the phase shift angle of the second power switch S 2 of all sub-modules SM of the two bridge arms of the primary side MMC
    Figure PCTCN2020134878-appb-100001
    Linear increase from 0 to π, the power transmitted from the primary side MMC to the secondary MMC increases from 0 to the maximum, and the corresponding power transmitted from the primary side MMC to the secondary MMC can be adjusted from 0 to the maximum;
    c)选择一次侧MMC向二次MMC传输的功率的大小，对二次侧子模块并联电容C进行充电；二次侧子模块并联电容C充电至二次侧电容标称电压V 2 *时结束充电。 c) Select the size of the power transmitted from the primary side MMC to the secondary MMC, and charge the secondary side sub-module parallel capacitor C; the secondary side sub-module parallel capacitor C is charged to the nominal voltage of the secondary side capacitor V 2 * . Charge.
  7. 根据权利要求4所述的一种多电平直流固态变压器多阶段软充控制方法，其特征在于，所述的一次侧电容标称电压V 1 *按照以下公式计算： The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 4, wherein the nominal voltage V 1 * of the primary side capacitor is calculated according to the following formula:
    Figure PCTCN2020134878-appb-100002
    Figure PCTCN2020134878-appb-100002
    其中，V 1 *一次侧电容标称电压；V dc1为输入源的电压，M为一次侧MMC每半桥臂子模块SM的个数。 Among them, V 1 * the nominal voltage of the primary side capacitor; V dc1 is the voltage of the input source, and M is the number of sub-modules SM per half bridge arm of the primary side MMC.
  8. 根据权利要求6所述的一种多电平直流固态变压器多阶段软充控制 方法，其特征在于，所述的二次侧电容标称电压V 2 *按照以下公式计算： The multi-stage soft charging control method of a multi-level DC solid-state transformer according to claim 6, wherein the nominal voltage V 2 * of the secondary side capacitor is calculated according to the following formula:
    Figure PCTCN2020134878-appb-100003
    Figure PCTCN2020134878-appb-100003
    其中，V 2 *一次侧电容标称电压；V dc2为输出源的电压，N为二次侧MMC每半桥臂子模块SM的个数。 Among them, V 2 * the nominal voltage of the primary side capacitor; V dc2 is the voltage of the output source, and N is the number of sub-modules SM per half bridge arm of the secondary side MMC.
  9. 一种多电平直流固态变压器多阶段软充控制系统，其特征在于，所述的模块化多电平直流固态变压器，包括输入源V dc1，输出源V dc2，一次侧MMC，二次侧MMC，限流电阻R d，限流开关S d，高频变压器T；所述的高频变压器T的漏感为L s；所述的一次侧MMC包含多个子模块SM构成H桥式电路；所述的二次侧MMC包含多个子模块SM构成H桥式电路；所述的一次侧MMC与二次侧MMC通过高频变压器T连接；所述的限流电阻R d与限流开关S d并联后一端与一次侧MMC连接，另一端与输入源V dc1连接；所述的输入源V dc1为直流源；输入源V dc1给一次侧MMC供电；所述的输出源V dc2为直流源或负载连接在二次侧MMC的输出端； A multi-stage soft charging control system for a multi-level DC solid-state transformer is characterized in that the modular multi-level DC solid-state transformer includes an input source V dc1 , an output source V dc2 , a primary side MMC, and a secondary side MMC , Current-limiting resistor Rd , current-limiting switch S d , high-frequency transformer T; the leakage inductance of the high-frequency transformer T is L s ; the primary-side MMC includes a plurality of sub-modules SM to form an H-bridge circuit; MMC said secondary side comprises a plurality of sub-modules constituting the H bridge circuit SM; the primary side and the secondary side MMC MMC connected by high-frequency transformer T; the current limiting resistor R d d in parallel with the current limiting switch S The rear end is connected to the primary side MMC, and the other end is connected to the input source V dc1 ; the input source V dc1 is a direct current source; the input source V dc1 supplies power to the primary side MMC; the output source V dc2 is a direct current source or load Connect to the output terminal of the secondary side MMC;
    所述的多阶段软充控制系统包括：模块一，一次侧MMC的子模块SM不控充电模块；模块二：使用峰值电流控制一次侧MMC的子模块SM软充电模块；模块三：使用移相调制控制二次侧MMC的子模块SM软充电模块。The multi-stage soft charging control system includes: module one, the sub-module SM of the primary side MMC does not control the charging module; module two: using the peak current to control the sub-module SM soft charging module of the primary side MMC; module three: using phase shifting Modulate and control the sub-module SM soft charging module of the secondary side MMC.
  10. 根据权利要求9所述的一种多电平直流固态变压器多阶段软充控制系统，其特征在于，所述的一次侧MMC还包含第一桥臂和第二桥臂；所述的一次侧MMC的第一桥臂和第二桥臂构成H桥结构；The multi-stage soft charging control system for a multi-level DC solid-state transformer according to claim 9, wherein the primary side MMC further comprises a first bridge arm and a second bridge arm; the primary side MMC The first bridge arm and the second bridge arm constitute an H bridge structure;
    所述的一次侧MMC的第一桥臂包含上半桥臂和下半桥臂；所述的一次侧MMC的第二桥臂也包含上半桥臂和下半桥臂；The first bridge arm of the primary side MMC includes an upper half bridge arm and a lower half bridge arm; the second bridge arm of the primary side MMC also includes an upper half bridge arm and a lower half bridge arm;
    所述的一次侧MMC的第一桥臂的上半桥臂包含M个子模块SM以及一个 第一桥臂上电感L a1，所述的M个子模块SM以及一个第一桥臂上电感L a1依次串联；所述的一次侧MMC的第一桥臂的下半桥臂包含M个子模块SM以及一个第一桥臂下电感L a2，所述的一次侧MMC的第一桥臂的下半桥臂的结构与所述的一次侧MMC的第一桥臂的上半桥臂的结构对称；对称点为a点； The upper half of the first bridge arm of the primary side MMC includes M sub-modules SM and an inductance La1 on the first bridge arm, and the M sub-modules SM and an inductance La1 on the first bridge arm are in turn series; lower half bridge arm of the first arm of the primary side of the MMC comprises M sub-module SM and the inductor L a2 next first bridge arm, the first arm of a half bridge arm lower side of the MMC The structure of is symmetrical with the structure of the upper half of the first bridge arm of the primary side MMC; the symmetry point is point a;
    所述的一次侧MMC的第二桥臂的上半桥臂包含M个子模块SM以及一个第二桥臂上电感L b1，所述的M个子模块SM以及一个第二桥臂上电感L b1依次串联；所述的一次侧MMC的第二桥臂的下半桥臂包含M个子模块SM以及一个第二桥臂下电感L b2，所述的一次侧MMC的第二桥臂的下半桥臂的结构与所述的一次侧MMC的第二桥臂的上半桥臂的结构对称；对称点为b点； The upper half of the second bridge arm of the primary side MMC includes M sub-modules SM and an inductance L b1 on the second bridge arm. The M sub-modules SM and the inductance L b1 on the second bridge arm are in turn In series; the lower half of the second leg of the primary side MMC includes M submodules SM and a second lower inductance L b2 , the lower half of the second leg of the primary side MMC The structure of is symmetrical with the structure of the upper half of the second bridge arm of the primary side MMC; the symmetry point is point b;
    所述的二次侧MMC包含第三桥臂和第四桥臂；所述的二次侧MMC的第三桥臂和第四桥臂构成H桥结构；The secondary side MMC includes a third bridge arm and a fourth bridge arm; the third bridge arm and the fourth bridge arm of the secondary side MMC constitute an H bridge structure;
    所述的二次侧MMC的第三桥臂包含上半桥臂和下半桥臂；所述的二次侧MMC的第四桥臂也包含上半桥臂和下半桥臂；The third bridge arm of the secondary side MMC includes an upper half bridge arm and a lower half bridge arm; the fourth bridge arm of the secondary side MMC also includes an upper half bridge arm and a lower half bridge arm;
    所述的二次侧MMC的第三桥臂的上半桥臂包含N个子模块SM以及一个第三桥臂上电感L c1，所述的N个子模块SM以及一个第三桥臂上电感L c1依次串联；所述的二次侧MMC的第三桥臂的下半桥臂包含N个子模块SM以及一个第三桥臂下电感L c2，所述的二次侧MMC的第三桥臂的下半桥臂的结构与所述的二次侧MMC的第三桥臂的上半桥臂的结构对称；对称点为c点； The upper half of the third bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L c1 on the third bridge arm, the N sub-modules SM and an inductance L c1 on the third bridge arm In series; the lower half of the third bridge arm of the secondary side MMC includes N sub-modules SM and a lower inductance L c2 of the third bridge arm, and the lower half of the third bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the third bridge arm of the secondary side MMC; the symmetry point is point c;
    所述的二次侧MMC的第四桥臂的上半桥臂包含N个子模块SM以及一个第四桥臂上电感L d1，所述的N个子模块SM以及一个第四桥臂上电感L d1依次串联；所述的二次侧MMC的第四桥臂的下半桥臂包含N个子模块SM以及一个第四桥臂下电感L d2，所述的二次侧MMC的第四桥臂的下半桥臂的结构 与所述的二次侧MMC的第四桥臂的上半桥臂的结构对称；对称点为d点； The upper half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and an inductance L d1 on the fourth bridge arm, the N sub-modules SM and an inductance L d1 on the fourth bridge arm In series; the lower half of the fourth bridge arm of the secondary side MMC includes N sub-modules SM and a fourth bridge arm lower inductance L d2 , the lower half of the fourth bridge arm of the secondary side MMC The structure of the half bridge arm is symmetrical to the structure of the upper half bridge arm of the fourth bridge arm of the secondary side MMC; the symmetry point is point d;
    所述的高频变压器T的四个端子分别与a点、b点、c点、d点连接。The four terminals of the high-frequency transformer T are respectively connected to point a, point b, point c, and point d.
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