WO2021196448A1 - 基于四端口模块化多电平变流器的贯通同相牵引供电系统 - Google Patents

基于四端口模块化多电平变流器的贯通同相牵引供电系统 Download PDF

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WO2021196448A1
WO2021196448A1 PCT/CN2020/102122 CN2020102122W WO2021196448A1 WO 2021196448 A1 WO2021196448 A1 WO 2021196448A1 CN 2020102122 W CN2020102122 W CN 2020102122W WO 2021196448 A1 WO2021196448 A1 WO 2021196448A1
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Prior art keywords
phase
traction
port
spc
transformer
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PCT/CN2020/102122
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English (en)
French (fr)
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林云志
魏应冬
李增勤
李笑倩
李明睿
张树卿
陆超
谢小荣
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中铁电气化局集团有限公司
清华大学
中铁电气工业有限公司
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Priority to EP20928166.6A priority Critical patent/EP4131762A4/en
Publication of WO2021196448A1 publication Critical patent/WO2021196448A1/zh

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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
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
    • B60M1/00—Power supply lines for contact with collector on vehicle
    • B60M1/12—Trolley lines; Accessories therefor
    • B60M1/13—Trolley wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
    • B60M3/00—Feeding power to supply lines in contact with collector on vehicles; Arrangements for consuming regenerative power
    • 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
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/297—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal for conversion of frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • 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
    • H02M1/0083—Converters characterised by their input or output configuration

Definitions

  • This application relates to a through-type in-phase traction power supply system, a traction substation and its power conversion device, in particular to a through-in-phase traction of a four-port modular multilevel converter suitable for three-phase-single-phase power conversion power supply system.
  • railway (rail transit) traction power supply system is the energy entrance of electrified railway and urban rail transit system, which is very important to the safety, stability and economy of its operation.
  • the traction power supply system of my country's high-speed, heavy-haul railway and inter-city rapid rail transit adopts the "single-phase 50Hz AC + unilateral power supply” system, and the "electric phase split" no-power zone shall be set every 10 ⁇ 30km interval, causing traffic failures The probability is greatly increased, the travel speed of high-speed rail is reduced, the efficiency of heavy-load transportation is reduced, and the neck is stuck in the locomotive.
  • In-phase traction power supply technology can be divided into three categories: quasi-in-phase traction power supply technology, virtual in-phase traction power supply technology and through-type in-phase traction power supply technology.
  • the quasi-in-phase traction power supply technology is a unilateral traction power supply system that uses a single-phase traction transformer or a single port of other traction transformers to supply power to the catenary. At the same time, it cooperates with active devices to compensate for the unbalanced power flow of the traction, such as patent 1.
  • Patent No. ZL201611056799.1 proposed a co-phase traction power supply system suitable for high-speed electrified railways
  • patent 2 Patent No. 201310227591.1 proposed a single-phase combined co-phase power supply and transformation structure.
  • the quasi-in-phase traction power supply technology cancels the electrical phase separation in the traction station, but because the bus voltage of the traction station cannot be directly controlled, the cancellation of the divisional power phase separation will form a low-voltage ring network and cause circulation. It is necessary to keep the separate phases of the power in the districts, making this technology not a complete in-phase power supply technology, so it is called a quasi-in-phase traction power supply technology.
  • the virtual in-phase traction power supply technology uses active devices to directly control the voltages of the traction stations and sub-stations in the phase-free area, without changing the power supply system of the existing traction power supply system.
  • Patent 3 Patent No. ZL201010596433.X
  • Patent 4 Patent No. ZL201010597237.4
  • Electrical over-phase-power quality comprehensive compensation device and method and patent 5 application number 201811313066.0
  • the virtual in-phase traction power supply technology has better solved the problem of the locomotive passing through the electrical phase separation, but it still belongs to the unilateral traction power supply system, and it also inherits the shortcomings of the unilateral power supply system, including: power supply capacity and reliability of power supply are limited, short-circuit failure Interaction with power quality; large voltage fluctuations in each section of the catenary, insufficient utilization of regenerative energy for traction locomotives, low utilization of traction variable capacity, and limited overall system reliability.
  • the through-type co-phase traction power supply technology is a bilateral traction power supply system, which mainly relies on the AC-to-AC conversion of the static power converter to realize the power conversion between the three-phase external power grid and the single-phase traction power grid. Its basic characteristics are:
  • the braking energy is controllably reduced and fed back to the three-phase system, making full use of the braking energy, which can save 10% to 20% of traction energy;
  • the core equipment to realize the through-type in-phase traction power supply technology is the three-phase/single-phase static power converter SPC. Its topology realization includes several typical methods:
  • Patent 6 proposes a single-phase unified power quality controller for electrified railway power supply. It is a single-phase AC-DC-single-phase AC unified power quality controller.
  • the multi-level independent DC link constructs the inverter side cascaded multi-level output, which can obtain good output voltage harmonic characteristics.
  • Document 1 I. Krastev, P. Tricoli, S. Hillmansen and M. Chen, "Future of Electric Railways: Advanced Electrification Systems with Static Converters for ac railways,"in IEEEElectrification Magazine,vol.4,no. 3,pp.6-14,Sept.2016. describes a similar structure, the difference is that each power unit on the rectifier side is a three-phase rectifier. The problem with this solution is that a more complex and costly multiple transformer is required.
  • the modular multi-level AC-to-AC direct converter MMDC technology is adopted to better solve the problems of the ABB and GE technical solutions.
  • the modular multi-level cascade mode of multiple H bridges is adopted to make SPC Harmonic characteristics and efficiency have been improved, and complicated transformer structures can be eliminated.
  • Siemens' MMDC technology requires that only when the SPC's input and output side grid frequencies are different, the power flow on the input and output sides can be decoupled from each other, and it is not suitable for 50Hz/50Hz application scenarios.
  • Level converter SPC is composed of three-phase MMC and single-phase MMC converters through the DC side interconnection, using multi-level technology to obtain good harmonic characteristics at the ports of the three-phase power grid and the single-phase traction network, and the input It is decoupled from the AC frequency of the output port and is suitable for different scenarios. But there are many bridge arms, insufficient utilization of switching power devices, and high overall cost.
  • the purpose of this application is to solve the problems of the existing three-phase/single-phase static power converter AC-AC converter topology, and construct a through-type in-phase traction substation and a through-type in-phase traction power supply system with economic advantages and excellent characteristics.
  • a through-type in-phase traction power supply system based on a four-port modular multilevel converter proposed in this application is characterized in that it is composed of a number of through-type in-phase traction substations arranged at intervals, and each through-type in-phase traction substation is The power source side of the substation is connected to the same synchronous public AC power grid, the load-side traction bus T-bus of each through-type in-phase traction substation is connected to the catenary T, and all traction substations on this side are connected to each other;
  • Each through-type in-phase traction substation includes a first traction transformer T 1 , a second traction transformer T 2 , a number of switches, and a static power converter SPC with three input ports Ac, Bc, Cc and one output port Xc;
  • the first traction transformer T 1 and the second traction transformer T 2 are both three-phase transformer structures, and the primary ports of each phase of the first traction transformer T 1 and the second traction transformer T 2 are respectively connected through three-phase circuit breakers CB1 and CB2.
  • the three phases A, B, and C into the synchronous public AC power grid, where the A phase leads the B phase by 120°, and the A phase lags the C phase by 120°.
  • Each of the first traction transformer T 1 and the second traction transformer T 2 The phase secondary ports are respectively connected to the three input ports Ac, Bc, Cc of the static power converter SPC through the three-phase circuit breakers CB6 and CB7, and the output port Xc of the static power converter is connected to the traction bus T-bus ,
  • the traction bus T-bus is connected to the catenary T through the single-phase circuit breaker CB3, and the rail is connected to the centralized ground terminal in the corresponding through-type in-phase traction substation through the return line;
  • the centralized ground terminal in the through-type in-phase traction substation is connected to the One input port of the static power converter SPC is connected, and the phase numbers of the input ports of the static power converter SPC in each through-type co-phase traction substation are connected to the centralized ground terminal of the station are the same;
  • the static power converter SPC is composed of k four-port modular multilevel converters 4P-MMC are composed in parallel.
  • Each four-port modular multilevel converter 4P-MMC includes four phases A, B, C, and X.
  • Each phase consists of The lower bridge arms are composed in series, the positive ends of the upper bridge arms of each phase are connected in parallel to form a DC positive electrode DC+, the negative ends of the lower bridge arms of each phase are connected in parallel to form a DC negative electrode DC-, the negative ends of the upper bridge arms of each phase and the positive ends of the lower bridge arms
  • the phases are connected in series as the midpoint of the corresponding phase, and the midpoints of the A, B, and C three-phases of each four-port modular multilevel converter 4P-MMC are connected to the corresponding static power converter SPC through a three-phase circuit breaker TB.
  • Input ports Ac, Bc, Cc, the X-phase midpoint of each four-port modular multilevel converter 4P-MMC is connected to the output port Xc of the static power converter SPC through the single-phase circuit breaker SB;
  • the effective value U L of the rated line voltage between the primary ports of the first traction transformer T 1 and the second traction transformer T 2 are equal, and the phase angles of the line voltages are sequentially different by 120°, and the rated line between the secondary ports
  • the effective voltage values U l are all equal, and the phase angles of the line voltages are sequentially different by 120°.
  • the transformation ratios of the first traction transformer T 1 and the second traction transformer T 2 are both K T :
  • each of the in-phase through the further traction substations each include a single-phase output transformer T o, the single-phase output transformer primary winding T o a corresponding access port P 1 through in-phase static power converter traction substation an output port SPC Xc, said static power converter according to any of the SPC via circuit breaker CB4 input port to access the single-phase output transformer primary winding T o another port P 0, in-phase and the through traction the single-phase output of the primary winding of the transformer T o access port P 0 is the static power converter with an input port number of the SPC are the same; the single-phase output transformer T o of the secondary winding S 1 through a single port
  • the phase circuit breaker CB5 is connected to the traction bus T-bus, and the other port S 0 is connected to the centralized grounding terminal in the corresponding through-type in-phase traction substation;
  • the rated voltage of the secondary side of the single-phase output transformer T o is the same as the rated voltage of the traction bus T-bus, and the effective value is U o .
  • the rated voltage of the primary side of the single-phase output transformer T o corresponds to the SPC output port of the static power converter Xc same port voltage, denoted valid values U x, the single-phase output transformer turns ratio K o T o is:
  • K o U o /U x .
  • the upper and lower bridge arms have the same structure, and they are respectively composed of several voltage source sub-modules and a filter reactor in series;
  • the positive terminal of the first voltage source submodule and one end of the filter reactor are respectively used as the positive and negative terminals of the upper bridge arm;
  • the lower bridge arm one end of the filter reactor and the end of the last voltage source submodule
  • the negative terminal serves as the positive terminal and the negative terminal of the lower bridge arm respectively.
  • Each through-type traction substation in the system of this application does not need to use a traction transformer with a special wiring form, but a conventional three-phase transformer, which has the advantages of simple wiring, low cost, and high capacity utilization.
  • SPC includes multiple 4P-MMCs running in parallel, some of which 4P-MMC failure exit does not affect the operation of SPC and through the same phase traction substation, the system operation reliability is high; two traction transformers can run in parallel, single transformer failure Affect the normal operation of the same-phase traction substation.
  • the four-port modular multilevel converter 4P-MMC constitutes the static power converter SPC of the core equipment of the in-phase traction substation.
  • the advantages of 4P-MMC include that, compared to the ABB and GE solutions, it avoids the large-capacity filter of the AC port, and at the same time avoids the complicated wiring of transformers on the three-phase AC and single-phase AC sides, which significantly improves system efficiency and reduces system costs.
  • 4P-MMC avoids the use of complex multiple transformers on the rectifier side, saves corresponding costs, and improves overall efficiency.
  • 4P-MMC solves the problem of its inability to adapt to the same frequency of input and output AC systems.
  • 4P-MMC maintains the excellent AC harmonic characteristics on both sides and the decoupling of input and output frequencies. At the same time, it eliminates a port and corresponding bridge arm.
  • the current stress of an input port is reduced, and the overall cost of power devices and capacitors can be reduced by 35%, which has strong economic advantages and high capacity utilization.
  • This application cancels the full-line electrical phase separation of the catenary, and relying on the SPC input port converter can effectively manage the power quality of the external public network and effectively limit the fault current of the catenary.
  • Fig. 1 is a schematic diagram of the overall structure of a through-type in-phase traction power supply system in an embodiment of the present application
  • Fig. 2 is a schematic structural diagram of a through-type in-phase traction substation without an output transformer in an embodiment of the present application;
  • FIG. 3 is a schematic diagram of the structure of a through-type in-phase traction substation containing an output transformer in an embodiment of the present application;
  • FIG. 4 is a schematic diagram of the structure of the i-th four-port modular multilevel converter 4P-MMC i in the static power converter SPC of the present application;
  • Fig. 5 is a schematic diagram of the upper and lower bridge arms of each phase constituting the four-port modular multilevel converter 4P-MMC in an embodiment of the present application;
  • Fig. 5(a) is a schematic diagram of the structure of the upper bridge arm, and
  • Fig. 5( b) is a schematic diagram of the structure of the lower bridge arm;
  • FIG. 6 is a schematic structural diagram of the voltage source sub-modules constituting each phase bridge arm in the 4P-MMC in an embodiment of the present application;
  • Fig. 7 is a voltage phasor diagram of the static power converter SPC of the present application.
  • Fig. 9 is a schematic structural diagram of a through-type in-phase traction substation that still has power supply capability after the SPC exits operation in an embodiment of the present application.
  • Fig. 1 is a through-cophase traction power supply system based on a four-port modular multilevel converter according to an embodiment of the present application.
  • a through-type co-phase traction power supply system based on a four-port modular multilevel converter consists of M (M is usually a positive integer greater than 1) separated by a certain distance (usually between 2km and 60km).
  • In-phase traction substation constitutes.
  • the external public grid connected to the power supply side of the M through-type in-phase traction substations shall belong to a synchronous AC power grid, and the load-side traction bus T-bus of the M through-type in-phase traction substations are all connected to the catenary T and The traction substations on this side are all connected to each other, and the traction power supply system is set up in separate phases without electricity.
  • Figure 2 is a through-type co-phase traction substation in an embodiment of the present application, including a three-phase conventionally connected first traction transformer T 1 , a three-phase conventionally connected second traction transformer T 2 , a group consisting of one or more A four-port modular multilevel converter 4P-MMC is connected in parallel to form a static power converter SPC and a number of switches.
  • a three-phase conventionally connected first traction transformer T 1 a three-phase conventionally connected second traction transformer T 2
  • a four-port modular multilevel converter 4P-MMC is connected in parallel to form a static power converter SPC and a number of switches.
  • the first traction transformer T 1 includes primary ports A 1 , B 1 , C 1 and secondary ports a 1 , b 1 , c 1 ;
  • the second traction transformer T 2 includes primary ports A 2 , B 2 , C 2 and Secondary ports a 2 , b 2 , c 2 ;
  • the static power converter SPC includes three input ports Ac, Bc, Cc and one output port Xc;
  • the switch includes three-phase circuit breakers CB1, CB2, CB6, CB7 and single-phase circuit breaker ⁇ CB3.
  • A, B, and C are used to represent the phase sequence of the three phases of the public AC power grid, where phase A leads phase B by 120° and phase A lags phase C by 120°.
  • connection relationship of the components in the through-type in-phase traction substation is as follows: the primary ports A 1 , B 1 , and C 1 of the first traction transformer T 1 are respectively connected to the synchronous public AC power grids A and B via the three-phase circuit breaker CB1 , C three-phase, the secondary side ports a 1 , b 1 , and c 1 of the first traction transformer T 1 are respectively connected to the three input ports Ac, Bc, Cc of the static power converter SPC through the three-phase circuit breaker CB6; the second traction The primary ports A 2 , B 2 , and C 2 of the transformer T 2 are respectively connected to the three-phase synchronous public AC grid A, B, and C via the three-phase circuit breaker CB2, and the secondary ports a 2 , b of the second traction transformer T 2 2.
  • the single-phase circuit breaker CB3 is connected to the contact network T, the rail is connected to the centralized ground terminal in the traction station through the return line, and the centralized ground terminal is connected to the earth network.
  • SPC configurable single-phase output transformer T o. 3 the original single-phase output windings of transformer T o a static access port P 1 of the power converter SPC output port Xc, three select inputs SPC Ac, Bc, Cc any one circuit breaker via CB4 access single-phase output transformer primary winding T o another port P 0, as shown in the access port Ac 3 P 0; and this application is the M-phase of the pulling-through output the single-phase transformer substation SPC SPC is the input port number with the primary winding T o access ports P 0 are the same.
  • One port S 1 of the secondary winding of the single-phase output transformer T o is connected to the traction bus T-bus via the circuit breaker CB5, and the other port S 0 is connected to the centralized grounding terminal.
  • the rated voltage of the secondary side of the single-phase output transformer T o is the same as the rated voltage of the traction bus T-bus, and the effective value is U o .
  • the rated voltage of the primary side of the single-phase output transformer T o is the same as the port voltage of the SPC output port Xc , referred to the effective value U x, the single-phase output transformer turns ratio K o T o is:
  • the three-phase conventional wiring traction transformers T 1 , T 2 the wiring form includes but not limited to YNd type, D yn type, Y yn type, Yd type, etc.
  • the common feature is: three ports on the primary side (A 1 , B 1 , C 1 or A 2 , B 2 , C 2 ), the effective value U L of the rated line voltage is the same, the phase angle of each line voltage differs by 120°, and the three ports on the secondary side (a 1 , The effective value U l of the rated line voltage between b 1 , c 1 or a 2 , b 2 , c 2 ) are all equal, and the phase angles of the line voltages differ by 120° in turn, and the traction transformer transformation ratio K T is:
  • Four-port modular multilevel converters are 4P-MMC i
  • the 4 ports of 4P-MMC i are denoted Ac i , Bc i , Cc i and Xc i .
  • 4P-MMC i Ac i input ports are input ports Ac access the SPC
  • 4P-MMC i Bc i input ports are input ports access the SPC Bc
  • an output port Xc 4P-MMC i are the i-access output port of Xc SPC.
  • the i-th four-port modular multilevel converter 4P-MMC i is shown in Fig. 4, including 4 phases A i , B i , C i , and X i , and each phase consists of upper and lower bridges
  • each phase consists of upper and lower bridges
  • the arms are connected in series, the positive terminal of the upper bridge arm of each phase is marked as P+, the negative terminal is marked as P-, the positive terminal of the lower bridge arm of each phase is marked as N+, and the negative terminal is marked as N-;
  • the positive terminal of each phase upper bridge arm is P+ parallel with each other, forming the DC positive DC +, each lower arm relative to the negative terminal of N- parallel to each other, forming the DC- DC negative electrode;
  • the first J i (J i A i , B i, C i, X i) relative to the upper arm
  • the negative terminal P- and the positive terminal N+ of the lower bridge arm form a J i phase midpoint Jm i (
  • the J i- phase upper arm of the i-th four-port modular multilevel converter 4P-MMC i is shown in Figure 5(a), consisting of N J voltage source sub-modules and a filter reactor L in series, the first of a voltage source submodule positive side as the positive terminal P J i with the upper arm +, each voltage source sub negative terminal of each module positive terminal connected to the lower voltage source sub-module, and finally a voltage source and the negative terminal of the sub-filter reactor is connected to one end of the module, the other end of the filter reactor as J i with the negative terminal P- of the arm.
  • the J i- phase lower arm of the i-th four-port modular multilevel converter 4P-MMC i is shown in Figure 5 (b), consisting of N J voltage source sub-modules and a filter reactor L sequentially in series, one end connected to the positive terminal of the filter reactor first voltage source sub-module and the other end of the filter reactor as J i with the n-terminal arm of N +, the negative terminal of each voltage source submodule are a lower voltage source positive terminal is connected to sub-module, a last negative terminal of voltage source submodule as J i with negative terminal of N- arm.
  • the voltage source sub-modules include but are not limited to the following power sub-module types:
  • the power electronic switch in it usually adopts reverse conducting IGBT or IGCT (which can be used alone or in combination).
  • the through-type co-phase traction power supply system proposed in this application adopts the direct power supply system, remember that the effective value of the rated voltage of the catenary T is U o , and the effective value of the rated line voltage of the through-type co-phase traction substation connected to the synchronous public AC grid is U L ,
  • the rated apparent capacity of the traction load of each through-type in-phase traction substation is S
  • the power factor angle of the traction load of the substation is ⁇ x .
  • the power factor angle of the end port is denoted as ⁇ , and the power factor angle is positive when the voltage lags behind the current.
  • the main electrical characteristics of SPC For other values of k, the main electrical quantities of the SPC are also set in the manner defined by formulas (4) to (20)).
  • the line voltages of the secondary ports of the traction transformers T 1 and T 2 are u ab , u bc , u ca , the virtual neutral point of the secondary port phase voltage is o, and the corresponding phase voltages are u ao , u bo , u co ,
  • the quantity is expressed as And take the voltage phasor
  • the voltage phasor diagram is shown in Figure 7, where U m is the effective value of the AC component of the upper and lower bridge arm voltages of A 1 , B 1 and C 1 in 4P-MMC 1 , and U xo is 4P-MMC X 1 in phase 1, the lower arm RMS voltage of the AC component, ⁇ xo upper 4P-MMC 1 X 1 in phase, the lower arm voltage of the AC component of the phase angle, U x to an output port Xc SPC voltage u xa ( The effective value of t), ⁇ x is the voltage phase angle of u xa (t).
  • the set of SPC-related electrical quantities and their reference directions are shown in FIG. 8.
  • the SPC input port Ac connected to the centralized ground terminal in Figure 2 as an example, the port Ac and the secondary side ports a 1 and a 2 of the traction transformer are both reference potentials, so relative to the reference potential (see point a in Figure 7), the SPC's
  • ⁇ is the angular frequency of the synchronous public AC power grid
  • t is the operating time of the system
  • U l is the effective value of the rated voltage between the secondary ports of the three-phase conventional traction transformer T 1 and T 2
  • U x is the output port Xc of the SPC voltage
  • u xa (t) is the effective value
  • u xa (t) is the voltage phase advance angle ⁇ x in the reference voltage phasors Is positive, generally select the value range of ⁇ x to satisfy:
  • U d be the rated DC voltage between 4P-MMC 1 DC positive DC+ and DC negative DC-, then U d should satisfy the relationship:
  • m is the three-phase modulation degree of A 1 , B 1 , and C 1.
  • a 1 , B 1 , C 1 , and X 1 phase upper and lower arm voltages of the 4P-MMC 1 in SPC are respectively:
  • the number of voltage source sub-modules N A , N B , N C , N X in the A 1 , B 1 , C 1 , X 1- phase upper and lower arms of the 4P-MMC 1 should satisfy the relationship:
  • record the currents of the SPC ports Ac, Bc, Cc, Xc that is, the currents of the A 1 , B 1 , C 1 , and X 1- phase AC ports of the 4P-MMC 1 are i a (t), i b (t) ,I c (t), i x (t); traction transformer T 1 or T 2 secondary port current i Ta (t), i Tb (t), i Tc (t) are positive sequence symmetrical currents, and their effective values Is I l ;
  • i a (t), i b (t), i c (t), i x (t) should satisfy the relationship:
  • I x is the effective value of i x (t).
  • S is the rated apparent capacity of the traction load of the through-type in-phase traction substation.
  • the A 1 , B 1 , C 1 , X 1 phase upper and lower arm currents of 4P-MMC 1 are respectively:
  • I da , I db , I dc , I dx are respectively the DC component of A 1 , B 1 , C 1 , and X 1 phase bridge arm current, which should satisfy:
  • the upper and lower arm currents of each phase of each 4P-MMC can be expressed as:
  • the SPC in this application is not equipped with an output single-phase transformer T o , the SPC output port Xc is directly connected to the traction bus T-bus in the through-type co-phase traction substation, and the effective value of the T-bus voltage and the effective value of the rated voltage of the catenary T are the same as U o , that is, satisfy:
  • M through-type in-phase traction substations jointly bear the traction load of the through-type traction catenary.
  • Traction transformers T 1 and T 2 can be used as a standby mode for each other. In this mode, when the through-type co-phase traction substation is in normal operation, if the first traction transformer T 1 is put into operation and T 2 is in standby, the three-phase circuit breakers CB1 and CB6 are closed. , CB2 and CB7 are disconnected.
  • the traction transformers T 1 and T 2 can adopt a parallel operation mode. In this mode, when the through-type co-phase traction substation operates normally, the first traction transformer T 1 and the second traction transformer T 2 are both put into operation, and the three-phase The circuit breakers CB1, CB2, CB6, CB7 are all closed. If the access line of the first traction transformer T 1 or its primary and secondary ports fails, CB1 and CB6 are disconnected, and the first traction transformer T 1 is taken out of operation; if the traction transformer T 2 or its primary and secondary ports access line failure, the breaking CB2, CB7, traction transformer T 2 of the second out of operation.
  • the k 4P-MMCs in a group of SPC of the through-type in-phase traction substation of this application equally share the traction load power, and the rated traction load power capacity allowed by each 4P-MMC is S/k. If a failure of the i-th converter 4P-MMC i in the SPC is detected, the 4P-MMC i medium power device trigger pulse should be immediately blocked, and the three-phase circuit breaker TB i and the single-phase circuit breaker SB i should be disconnected, and the SPC remains The k-1 4P-MMCs equally share the traction load power; accordingly, the traction load rated power capacity allowed by the traction substation is reduced to (k-1)S/k.
  • each traction substation When no more than k-1 4P-MMCs in a group of SPC of the through-type co-phase traction substation fail, the traction substation is still running in the through-type co-phase traction power supply system.
  • the through-type in-phase traction substation has k 4P-MMCs in a group of SPC failures, the through-type in-phase traction substation fails and exits operation, and the remaining M-1 traction substations of the through-type in-phase traction power supply system are redistributed and passed.
  • the power capacity of each traction substation does not affect the normal operation of the through-type traction power supply system; each through-type in-phase traction substation shall have a certain redundant power capacity.
  • the three-phase circuit breaker TB i and the single-phase circuit breaker SB i of each 4P-MMC of the SPC are disconnected, and the circuit breaker CB8 is then closed, and the three-phase traction transformer T 1 or T 2 secondary side b 1 (b 2 ) port or c 1 (c 2 ) port directly supplies power to the traction bus T-bus to save the power capacity of other through-type co-phase traction substations, and the through-connection should be adjusted at the same time
  • the SPC output voltage of the remaining M-1 through-type in-phase traction substations in the in-phase in-phase traction power supply system tracks the voltage at the ports b 1 (b 2 ) or c 1 (c 2 ) of the traction substation.
  • the traction transformers T 1 and T 2 are both connected with YNd type
  • the static power converter SPC is configured to output a single-phase transformer T o .
  • the number of four-port modular multilevel converter 4P-MMC k 1.
  • the effective value of the rated line voltage of the synchronous public AC power grid U L 110kV
  • the effective value of the rated line voltage of the secondary side of the traction transformer U l 27.5kV
  • the transformation ratio K T of the traction transformer is:
  • phase angle ⁇ x of the SPC output port voltage u xa (t) ⁇
  • effective value U x of the voltage at the SPC output port Xc is :
  • the effective value U m of the AC component of the upper and lower bridge arm voltages in the A 1 , B 1 , and C 1 phases of 4P-MMC 1 is:
  • the effective value U xo and the phase angle ⁇ xo of the AC component of the upper and lower arm voltages of the X 1 phase are:
  • the number of source sub-modules N A , N B , N C , N X should satisfy:
  • the sum of the capacity (effective value) of each bridge arm of the 4P-MMC is 188.8MVA, and the sum of the capacity (peak value) of each bridge arm is 326.4MVA; The sum of) is 289.2MVA, and the sum of each bridge arm capacity (peak value) is 498.4MVA.
  • the 4P-MMC proposed in this application can reduce the cost of power devices and capacitors by 35% as a whole.

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Abstract

本申请提出的一种基于四端口模块化多电平变流器的贯通同相牵引供电系统，由多个贯通式同相牵引变电所牵引母线接入相互连通的接触网组成，各贯通式同相牵引变电所包括两个牵引变压器T1和T2、具有三个输入端口和一个输出端口的静止功率转换器SPC；T1和T2 的三相原边端口由断路器接入同步公共交流电网的三相，T1和T2的三相副边端口均分别接入SPC的三个输入端口，SPC的输出端口接入牵引母线；SPC由k个四端口模块化多电平变流器4P-MMC并联组成，各4P-MMC均分别包括四相，每相由上下桥臂串联组成，各4P-MMC的三相中点分别通过三相断路器接入SPC的对应输入端口，各4P-MMC的第四相中点分别由断路器接入SPC的输出端口。本申请具有取消接触全网电分相，变电所牵引变压器接线简单，系统设备容量利用率高、配置灵活、可靠性高、成本低的优势。

Description

基于四端口模块化多电平变流器的贯通同相牵引供电系统
相关申请的交叉引用
本申请要求清华大学于2020年04月04日提交的、发明名称为“基于四端口模块化多电平变流器的贯通同相牵引供电系统”的、中国专利申请号“202010261430.4”的优先权。
技术领域
本申请涉及一种贯通式同相牵引供电系统、牵引变电所及其功率转换装置，特别是一种适于三相-单相功率变换的四端口模块化多电平变流器的贯通同相牵引供电系统。
背景技术
铁路(轨道交通)牵引供电系统是电气化铁路和城市轨道交通系统的能源入口，对其运行的安全稳定性和经济性至关重要。我国高速、重载铁路以及城际快速轨道交通的牵引供电系统，均采用“单相50Hz交流+单边供电”制式，每间隔10～30km须设置“电分相”无电区，造成行车故障概率大大增加、高铁旅行速度下降、重载运输效率降低以及机车“趴窝”等卡脖子难题。此外，既面临诸多影响公网的严重电能质量问题，还存在牵引机车再生能量利用不足、牵引变容量利用率低下、系统整体可靠性有限等痼疾。现行牵引供电制式的“电分相”始终制约我国电气化铁路的安全、可靠、高效、高品质运行，解决该问题的核心是同相牵引供电技术。
同相牵引供电技术可分为准同相牵引供电技术、虚拟同相牵引供电技术和贯通式同相牵引供电技术三大类。
准同相牵引供电技术是一种单边牵引供电制式，通过在牵引所采用单相牵引变压器或其他牵引变压器的单一端口为接触网供电，同时配合有源装置补偿牵引所不平衡潮流，如专利1(专利号ZL201611056799.1)提出的一种适用于高速电气化铁路的同相牵引供电系统和专利2(专利号201310227591.1)提出的一种单相组合式同相供变电构造。准同相牵引供电技术取消了牵引所内电分相，但由于无法直接控制牵引所母线电压，取消分区所电分相会构成低压环网引起环流。不得不保留分区所电分相，使得该技术不是完全的同相供电技术，故称为准同相牵引供电技术。
虚拟同相牵引供电技术利用有源装置直接控制牵引所和分区所中电分相无电区电压，在不改变既有牵引供电系统供电制式的基础上，实现机车无断电通过全接触网电分相，如 专利3(专利号ZL201010596433.X)提出的一种牵引网电分相无断电柔性连接-补偿装置及其方法、专利4(专利号ZL201010597237.4)提出的一种电力机车无断电过分相-电能质量综合补偿装置及其方法和专利5(申请号201811313066.0)提出的一种分区所无断电柔性电分相设备及其控制方法。虚拟同相牵引供电技术较好地解决了机车通过电分相的问题，但仍属于单边牵引供电制式，也继承了单边供电制式的缺点，包括：供电能力与供电可靠性受限，短路故障和电能质量相互影响；接触网各段电压波动大，牵引机车再生能量利用不足、牵引变容量利用率低下、系统整体可靠性有限等痼疾。
贯通式同相牵引供电技术是双边牵引供电制式，主要依靠静止功率转换器的交交变换，实现三相外部电网与单相牵引电网的功率转换，其基本特点为：
1)完全取消电分相，实现真正同相供电，机车在接触网运行全过程无需过分相操作，安全可靠，无速度损失；
2)确保外部电力系统三相系统平衡，无需动态无功补偿，谐波达标；
3)三相电网与牵引系统完全解耦，几乎互不影响、电网故障穿越能力强；
4)牵引变压器容量利用率高，牵引所固定容量和运行费用降低；
5)外部的电源短路容量要求低、降低开关设备造价、电网适应能力强；
6)实现双边供电，供电能力强，有利于增大牵引站间距，稳定接触网电压，有效提高供电可靠性；
7)牵引系统故障电流限制，接触网短路时电流迅速限制在额定值以内，降低接地及连接机构造价；
8)制动能量可控地减少回馈至三相系统，充分利用制动能量，可节省牵引能量10％～20％；
实现贯通式同相牵引供电技术的核心装备是三相/单相静止功率转换器SPC，其拓扑实现包括几种典型方式：
1)以ABB和GE等公司为代表，采用基于三电平的三相交流-直流-单相交流变换方案。两侧变流器通过共同的直流环节相互连接，其逆变通常采用单相变压器串联多重化方式以减小输出电压谐波，典型型号为PCS-6000Rail。由于该方案电平数较少，等效开关频率有限，需要复杂的多重化变压器降低特征频率，变压器绕制复杂；交流电压、电流谐波较大，器件容量要求高，效率较低，并且需要增加较大的滤波器。
2)专利6(专利号：ZL200710175253.2)提出了一种用于电气化铁路供电的单相统一电能质量控制器，是一种单相交流-直流-单相交流的统一电能质量控制器，利用多级独立直流环节构造出逆变侧级联多电平输出，可获得良好的输出电压谐波特性。类似地，文献1(I.Krastev,P.Tricoli,S.Hillmansen and M.Chen,"Future of Electric Railways:Advanced  Electrification Systems with Static Converters for ac Railways,"in IEEE Electrification Magazine,vol.4,no.3,pp.6-14,Sept.2016.)描述了类似结构，区别在于整流侧各功率单元为三相整流器。该方案的问题在于需要较为复杂、成本较高的多重化变压器。
3)以西门子为代表，采用模块化多电平交交直接变换器MMDC技术，较好地解决了ABB和GE技术方案的问题，采用多个H桥的模块化多电平级联方式，使得SPC谐波特性和效率均得到提升，可省去复杂的变压器结构。然而，西门子的MMDC技术要求，只有当SPC的输入和输出侧电网频率不同时，其输入与输出侧的功率潮流才能相互解耦，并不适合应用于50Hz/50Hz的应用场景。
4)文献2(Winkelnkemper M，Korn A，Steimer P.A modular direct converter for transformerless rail interties[A].IEEE International Symposium on Industrial Electronics[C].2010.562-567.)描述的交-直-交型模块化多电平变流器SPC，采用三相MMC和单相MMC变流器通过直流侧互联构成，利用多电平技术，在三相电网和单相牵引网端口获得了良好的谐波特性，并且输入与输出端口交流频率相互解耦，适用于不同场景。但存在桥臂较多，开关功率器件利用率不足，总体成本高的缺陷。
发明内容
本申请的目的在于解决既有三相/单相静止功率转换器交交变换变流器拓扑存在的问题，构造有经济优势、特性优良的贯通式同相牵引变电所及贯通式同相牵引供电系统。
为了实现上述目的，本申请采用如下技术方案：
本申请提出的一种基于四端口模块化多电平变流器的贯通同相牵引供电系统，其特征在于，由若干个间隔设置的贯通式同相牵引变电所组成，各贯通式同相牵引变电所的电源侧接入同一同步公共交流电网，各贯通式同相牵引变电所的负荷侧牵引母线T-bus均接入接触网T且该侧所有牵引变电所之间全部相互贯通；
各贯通式同相牵引变电所包括第一牵引变压器T 1、第二牵引变压器T 2、若干开关以及具有三个输入端口Ac、Bc、Cc和一个输出端口Xc的静止功率转换器SPC；所述第一牵引变压器T 1和第二牵引变压器T 2均为三相变压器结构，所述第一牵引变压器T 1和第二牵引变压器T 2的各相原边端口分别通过三相断路器CB1、CB2接入同步公共交流电网的A、B、C三相，其中A相超前于B相120°、A相滞后于C相120°，所述第一牵引变压器T 1和第二牵引变压器T 2的各相副边端口分别通过三相断路器CB6和CB7均接入所述静止功率转换器SPC的三个输入端口Ac、Bc、Cc，该静止功率转换器的输出端口Xc接入牵引母线T-bus，牵引母线T-bus通过单相断路器CB3接入接触网T，铁轨通过回流线接入相应贯通式同相牵引变电所内集中接地端；所述贯通式同相牵引变电所内集中接地端与静止功率转 换器SPC的一个输入端口相连接，且各个贯通式同相牵引变电所内集中接地端接入该所的静止功率转换器SPC的输入端口相序号均相同；所述静止功率转换器SPC由k个四端口模块化多电平变流器4P-MMC并联组成，各四端口模块化多电平变流器4P-MMC均分别包括A、B、C、X四相，每相由上、下桥臂串联组成，各相上桥臂正极端相互并联形成直流正极DC+，各相下桥臂负极端相互并联形成直流负极DC-，各相上桥臂的负极端和下桥臂的正极端相串联作为对应相的中点，各四端口模块化多电平变流器4P-MMC的A、B、C三相中点分别通过一三相断路器TB接入静止功率转换器SPC的对应输入端口Ac、Bc、Cc，各四端口模块化多电平变流器4P-MMC的X相中点分别通过单相断路器SB接入静止功率转换器SPC的输出端口Xc；
所述第一牵引变压器T 1和第二牵引变压器T 2的各原边端口间的额定线电压有效值U L均相等、各线电压相角依次相差120°，各副边端口间的额定线电压有效值U l均相等、各线电压相角依次相差120°，第一牵引变压器T 1和第二牵引变压器T 2变比均为K T：
K T＝U l/U L。
进一步地，各贯通式同相牵引变电所还均分别包括单相输出变压器T o，该单相输出变压器T o的原边绕组一端口P 1接入相应贯通式同相牵引变电所内静止功率转换器SPC的输出端口Xc，所述静止功率转换器SPC的任一输入端口经断路器CB4接入所述单相输出变压器T o的原边绕组另一端口P 0，且各贯通式同相牵引变电所内单相输出变压器T o原边绕组端口P 0接入的该所静止功率转换器SPC的输入端口相序号均相同；所述单相输出变压器T o的副边绕组一端口S 1经单相断路器CB5接入牵引母线T-bus，另一端口S 0接入相应贯通式同相牵引变电所内集中接地端；
所述单相输出变压器T o的副边额定电压与牵引母线T-bus额定电压相同，记有效值为U o，单相输出变压器T o的原边额定电压与对应静止功率转换器SPC输出端口Xc的端口电压相同，记有效值为U x，则单相输出变压器T o变比K o为：
K o＝U o/U x。
进一步地，各四端口模块化多电平变流器4P-MMC的各相中，上、下桥臂结构相同，均分别由若干个电压源子模块以及一台滤波电抗器依次串联组成；上桥臂中，第一个电压源子模块的正极端和滤波电抗器的一端分别作为上桥臂的正极端和负极端；下桥臂中，滤波电抗器的一端和最后一个电压源子模块的负极端分别作为下桥臂的正极端和负极端。
本申请提出的贯通同相牵引供电系统，其特点及有益效果在于：
1)本申请系统中各贯通式牵引变电所不需采用特殊接线形式的牵引变压器，而是采用常规三相变压器，该变压器具有接线简单、成本低、容量利用率高的优势。
2)SPC包括多台4P-MMC并列运行，其中部分4P-MMC故障退出不影响SPC及贯通 同相牵引变电所运行，系统运行可靠性高；两台牵引变压器可并列运行，单台变压器故障不影响贯通同相牵引变电所正常运行。
3)提出四端口模块化多电平变流器4P-MMC构成本申请系统贯通同相牵引变电所核心设备静止功率转换器SPC。4P-MMC的优势包括，相对于ABB、GE的方案，避免了交流端口较大容量滤波器，同时可避免在三相交流和单相交流侧复杂接线变压器，显著提高系统效率并降低系统成本。4P-MMC相对于专利6和文献1所述方案，避免了整流侧采用复杂多重化变压器，节省了相应地成本，提高了整体效率。4P-MMC相对于西门子MMDC技术，解决了其无法适应输入和输出交流系统为相同频率的应用场景问题。4P-MMC相对于文献2所述五端口交-直-交型MMC方案，在保持两侧交流谐波特性优良，输入输出频率解耦的特点同时，由于省去了一个端口及相应桥臂，并且减小了一个输入端口的电流应力，整体可降低35％的功率器件和电容成本，具有很强的经济优势和高容量利用率。
4)本申请取消接触网全线电分相，依赖SPC输入端口变流器可对外部公网电能质量有效治理，并有效限制接触网故障电流。
本发明附加的方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本申请反馈的实践了解到。
附图说明
本申请反馈上述的和/或附加的方面和优点从下面结合附图对实施例的描述中将变得明显和容易理解，其中：
图1是本申请实施例中贯通式同相牵引供电系统的整体结构示意图；
图2是本申请实施例中不含输出变压器的贯通式同相牵引变电所的结构示意图；
图3是本申请实施例中含有输出变压器的贯通式同相牵引变电所的结构示意图；
图4是本申请的静止功率转换器SPC中第i个四端口模块化多电平变流器4P-MMC i的结构示意图；
图5是本申请实施例中构成四端口模块化多电平变流器4P-MMC的各相上、下桥臂结构示意图；其中图5(a)是上桥臂的结构示意图，图5(b)是下桥臂的结构示意图；
图6是本申请实施例中构成4P-MMC中各相桥臂的电压源子模块的结构示意图；
图7是本申请的静止功率转换器SPC的电压相量图；
图8是本申请的静止功率转换器SPC(k＝1)的电气结构及关键电气量示意图；
图9是本申请实施例中一种在SPC退出运行后仍具备供电能力的贯通式同相牵引变电所的结构示意图。
具体实施方式
下面详细描述本申请的实施例，实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，旨在用于解释本申请，而不能理解为对本申请的限制。
下面参照附图描述根据本申请实施例提出的基于四端口模块化多电平变流器的贯通式同相牵引供电系统。
图1是本申请的一个实施例的基于四端口模块化多电平变流器的贯通同相牵引供电系统。
如图1所示，基于四端口模块化多电平变流器的贯通式同相牵引供电系统，由M个(M通常为大于1的正整数)间隔一定距离(通常在2km～60km)的贯通式同相牵引变电所构成。本申请中M个贯通式同相牵引变电所电源侧接入的外部公共电网应属于一个同步交流电网，M个贯通式同相牵引变电所负荷侧牵引母线T-bus均接入接触网T且该侧各牵引变电所之间全部相互贯通，牵引供电系统全线无电分相设置。图2是本申请的一个实施例中一个贯通式同相牵引变电所，包括一个三相常规接线第一牵引变压器T 1，一个三相常规接线第二牵引变压器T 2，一组由一个或多个四端口模块化多电平变流器4P-MMC并联组成的静止功率转换器SPC和若干开关。第一牵引变压器T 1包括原边端口A 1、B 1、C 1和副边端口a 1、b 1、c 1；第二牵引变压器T 2包括原边端口A 2、B 2、C 2和副边端口a 2、b 2、c 2；静止功率转换器SPC包括三个输入端口Ac、Bc、Cc和一个输出端口Xc；开关包括三相断路器CB1、CB2、CB6、CB7和单相断路器CB3。采用A、B、C表示该公共交流电网三相中各相序，其中A相超前于B相120°、A相滞后于C相120°。所述贯通式同相牵引变电所内各元件的连接关系为：第一牵引变压器T 1的原边端口A 1、B 1、C 1经三相断路器CB1分别接入同步公共交流电网A、B、C三相，第一牵引变压器T 1的副边端口a 1、b 1、c 1分别通过三相断路器CB6接入静止功率转换器SPC三个输入端口Ac、Bc、Cc；第二牵引变压器T 2的原边端口A 2、B 2、C 2经三相断路器CB2分别接入同步公共交流电网A、B、C三相，第二牵引变压器T 2的副边端口a 2、b 2、c 2分别通过三相断路器CB7接入静止功率转换器SPC三个输入端口Ac、Bc、Cc；静止功率转换器SPC的输出端口Xc接入牵引母线T-bus，牵引母线T-bus经单相断路器CB3接入接触网T，铁轨经回流线接入牵引所内集中接地端，所述集中接地端接入大地地网。
选择牵引所内集中接地端接入SPC三个输入端口Ac、Bc、Cc中的一个，如图2中端口Ac接入集中接地端；并且，本申请M个所述贯通式同相牵引变电所内集中接地端接入的该所SPC的输入端口相序号均相同。
可选地，SPC可配置单相输出变压器T o。如图3所示，单相输出变压器T o的原边绕组一端口P 1接入静止功率转换器SPC的输出端口Xc，选择SPC三个输入端口Ac、Bc、Cc中的任一个经断路器CB4接入单相输出变压器T o的原边绕组另一端口P 0，如图3中端口Ac接入P 0；并且，本申请M个所述贯通式同相牵引变电所内SPC输出单相变压器T o原边 绕组端口P 0接入的该所SPC的输入端口相序号均相同。单相输出变压器T o的副边绕组一端口S 1经断路器CB5接入牵引母线T-bus，另一端口S 0接入集中接地端。可选择静止功率转换器SPC三个输入端口Ac、Bc、Cc和输出端口Xc中任一端口接入集中接地箱，或者选择四个端口均不接入集中接地箱。
其中，单相输出变压器T o的副边额定电压与牵引母线T-bus额定电压相同，记有效值为U o，单相输出变压器T o的原边额定电压与SPC输出端口Xc的端口电压相同，记有效值为U x，则单相输出变压器T o变比K o为：
K o＝U o/U x      (1)
进一步地，所述三相常规接线牵引变压器T 1、T 2，接线形式包括但不限于YNd型，D yn型，Y yn型，Yd型等，其共同特征为：原边三个端口(A 1、B 1、C 1或A 2、B 2、C 2)间的额定线电压有效值U L均相等、各线电压相角依次相差120°，副边三个端口(a 1、b 1、c 1或a 2、b 2、c 2)间的额定线电压有效值U l均相等、各线电压相角依次相差120°，牵引变压器变比K T为：
K T＝U l/U L      (2)
一组所述静止功率转换器SPC，通常包括k个(通常k∈[1，6]的自然数)相同的四端口模块化多电平变流器4P-MMC，记第i(i＝1,2,…,k)个四端口模块化多电平变流器为4P-MMC i，且4P-MMC i的4个端口记为Ac i、Bc i、Cc i和Xc i。4P-MMC i的输入端口Ac i均接入SPC的输入端口Ac，4P-MMC i的输入端口Bc i均接入SPC的输入端口Bc，4P-MMC i的输入端口Cc i均接入SPC的输入端口Cc，4P-MMC i的输出端口Xc i均接入SPC的输出端口Xc。
所述第i个四端口模块化多电平变流器4P-MMC i如图4所示，包括A i、B i、C i、X i共4相，每相由上、下两个桥臂相互串联而成，各相上桥臂正极端记为P+、负极端记为P-，各相下桥臂正极端记为N+、负极端记为N-；各相上桥臂正极端P+相互并联，形成直流正极DC+，各相下桥臂负极端N-相互并联，形成直流负极DC-；其中第J i(J i＝A i,B i,C i,X i)相上桥臂负极端P-与下桥臂正极端N+构成J i相中点Jm i(Jm i＝Am i,Bm i,Cm i,Xm i)。其中Am i、Bm i、Cm i经过三相断路器TB i对应接入4P-MMC i的输入端口Ac i、Bc i、Cc i，而Xm i经过单相断路器SB i接入4P-MMC i的输出端口Xc i。
所述第i个四端口模块化多电平变流器4P-MMC i的J i相上桥臂如图5中(a)所示，由N J个电压源子模块以及一台滤波电抗器L依次串联组成，第一个电压源子模块的正极端作为J i相上桥臂的正极端P+，每一个电压源子模块的负极端均与下一个电压源子模块的正极端相连，最后一个电压源子模块的负极端与滤波电抗器的一端相连，滤波电抗器的另一端作为J i相上桥臂的负极端P-。
所述第i个四端口模块化多电平变流器4P-MMC i的J i相下桥臂如图5中(b)所示，由 N J个电压源子模块以及一台滤波电抗器L依次串联组成，第一个电压源子模块的正极端与滤波电抗器的一端相连，滤波电抗器的另一端作为J i相下桥臂的正极端N+，每一个电压源子模块的负极端均与下一个电压源子模块的正极端相连，最后一个电压源子模块的负极端作为J i相下桥臂的负极端N-。
所述电压源子模块均为单相电压源型变流器结构，具有g(g为正整数且满足g≥2)个输出电平；记电压源子模块交流正、负极间电压为u SM，流经电压源子模块的电流为i SM，且均以电压源子模块正极端到负极端为正方向，参见图6；所述电压源子模块中包括f个直流电容(f为正整数且满足g>f≥1)，其中电压源子模块内第v个直流电容正极与负极之间的电压差为该直流电容的直流电压U cv(v＝1,2,…，f)，电压源子模块额定直流电压U c通常满足关系：
Figure PCTCN2020102122-appb-000001
在电压源子模块内部所有电力电子开关受控关断时，若流经电压源子模块的电流i SM方向为负，则电压源子模块端口电压u SM幅值近似为零。
所述电压源子模块包括但不限于以下功率子模块类型：
半桥子模块(简称HBSM)，记为A 1型电压源子模块，对应g＝2、f＝1；双半桥子模块记为A 2型电压源子模块，对应g＝3、f＝2；带阻断开关的T型中点箝位子模块记为A 3型电压源子模块，对应g＝3、f＝2；飞跨电容型三电平子模块记为A 4型电压源子模块，对应g＝3、f＝2；所述A 1—A 4型子模块均为公知的标准电路，其中A 2、A 3、A 4参见文献(Nami,A.,et al.,Modular Multilevel Converters for HVDC Applications:Review on Converter Cells and Functionalities.IEEE Transactions on Power Electronics,2015.30(1):p.18-36.)。
所述电压源子模块，其中的电力电子开关通常采用逆导型IGBT或IGCT(可单独使用或混用)。
若本申请提出的贯通式同相牵引供电系统采用直接供电制式，记接触网T额定电压有效值为U o，贯通式同相牵引变电所接入同步公共交流电网额定线电压有效值为U L，每个贯通式同相牵引变电所牵引负荷额定视在容量为S，变电所牵引负荷功率因数角为φ x，贯通式同相牵引变电所注入同步公共交流电网端口为正序电流，其近端端口功率因数角记为φ，功率因数角均以电压滞后于电流为正。以所述贯通式同相牵引变电所中的一组静止功率转换器SPC所包含的四端口模块化多电平变流器4P-MMC的数量k＝1为例，说明SPC主要电气量特征(对于k取其他数值的情况，SPC主要电气量同样按照公式(4)～(20)所限定的方式进行设置)。
记牵引变压器T 1、T 2副边端口线电压均为u ab，u bc，u ca，副边端口相电压虚拟中性点为o，对应相电压为u ao，u bo，u co，相量形式表示为
Figure PCTCN2020102122-appb-000002
并以电压相量
Figure PCTCN2020102122-appb-000003
为参考相位，其电压相量图如图7所示，其中U m为4P-MMC 1中A 1，B 1，C 1相上、下桥臂电 压交流分量有效值，U xo为4P-MMC 1中X 1相上、下桥臂电压交流分量有效值，δ xo为4P-MMC 1中X 1相上、下桥臂电压交流分量相位角，U x为SPC的输出端口Xc电压u xa(t)的有效值，δ x为u xa(t)的电压相位角。
所述一组SPC相关电气量及其参考方向如图8所示。以图2中SPC输入端口Ac接入集中接地端为例，端口Ac和牵引变压器的副边端口a 1和a 2均为参考电位，则相对参考电位(见图7中a点)，SPC的输入端口Ac、Bc、Cc、输出端口Xc的电压，即4P-MMC 1变流器的A 1，B 1，C 1，X 1相交流端口电压u aa(t)，u ba(t)，u ca(t)，u xa(t)可分别表示为：
Figure PCTCN2020102122-appb-000004
式中，ω为同步公共交流电网的角频率，t为系统运行时间，U l为三相常规牵引变压器T 1、T 2副边端口线间额定电压有效值，U x为SPC的输出端口Xc电压u xa(t)的有效值，u xa(t)的电压相位角δ x以超前于参考电压相量
Figure PCTCN2020102122-appb-000005
为正，一般选取δ x取值范围满足：
Figure PCTCN2020102122-appb-000006
在本申请中，通常选择SPC输出端口电压u xa(t)的相位角δ x＝π。
4P-MMC 1中A 1，B 1，C 1相上、下桥臂电压交流分量有效值均为U m，应满足：
Figure PCTCN2020102122-appb-000007
记U d为4P-MMC 1直流正极DC+与直流负极DC-之间的额定直流电压，则U d应满足关系：
Figure PCTCN2020102122-appb-000008
式中m为A 1，B 1，C 1三相调制度。
4P-MMC 1中X 1相上、下桥臂电压交流分量有效值U xo、交流分量相位角δ xo，应满足：
Figure PCTCN2020102122-appb-000009
记X 1相调制度为m x，应满足关系：
Figure PCTCN2020102122-appb-000010
通常选择m、m x∈[0.8,0.95]。
进一步有，SPC中4P-MMC 1的A 1，B 1，C 1，X 1相上、下桥臂电压分别为：
Figure PCTCN2020102122-appb-000011
对应地，4P-MMC 1的A 1，B 1，C 1，X 1相上、下桥臂中电压源子模块的数量N A，N B，N C，N X应满足关系式：
Figure PCTCN2020102122-appb-000012
如图8，记SPC的端口Ac、Bc、Cc、Xc电流，即4P-MMC 1的A 1，B 1，C 1，X 1相交流端口电流为i a(t)，i b(t)，i c(t)，i x(t)；牵引变压器T 1或T 2副边端口电流i Ta(t)，i Tb(t)，i Tc(t)为正序对称电流，其有效值为I l；
则有关系式：
Figure PCTCN2020102122-appb-000013
详细地，i a(t)，i b(t)，i c(t)，i x(t)应满足关系式：
Figure PCTCN2020102122-appb-000014
式中I x为i x(t)的有效值。
根据能量守恒定律，且不考虑SPC损耗，则应满足：
Figure PCTCN2020102122-appb-000015
式中，S为贯通式同相牵引变电所牵引负荷额定视在容量。
4P-MMC 1的A 1，B 1，C 1，X 1相上、下桥臂电流分别为：
Figure PCTCN2020102122-appb-000016
式中，I da、I db、I dc、I dx分别为A 1，B 1，C 1，X 1相桥臂电流的直流分量，应满足：
Figure PCTCN2020102122-appb-000017
一般地，当SPC由k个相同规格4P-MMC并联时，每个4P-MMC各相上、下桥臂电流可表示为：
Figure PCTCN2020102122-appb-000018
特别地，当4P-MMC各相调制度满足m＝m x(对于4P-MMC个数大于1的情况，单个 4P-MMC内各相调制度应相等)时，其各相桥臂容量利用率最大，对于SPC典型工作点δ x＝π，U l与U x应满足关系：
Figure PCTCN2020102122-appb-000019
若本申请SPC不配置输出单相变压器T o，SPC输出端口Xc直接接入贯通式同相牵引变电所内牵引母线T-bus，T-bus电压有效值与接触网T额定电压有效值同为U o，即满足：
U x＝U o      (19)
若本申请SPC配置输出单相变压器T o，且U l＝U o，则单相输出变压器T o的变比K o应满足：
Figure PCTCN2020102122-appb-000020
本申请贯通式同相牵引供电系统的工作原理如下：
本申请贯通式同相牵引供电系统正常运行时，M个贯通式同相牵引变电所共同承担贯通式牵引接触网全线牵引负荷。
牵引变压器T 1与T 2可采用互为备用方式，该方式下贯通式同相牵引变电所正常运行时，若第一牵引变压器T 1投运、T 2备用，三相断路器CB1、CB6闭合，CB2、CB7断开。若第一牵引变压器T 1或其原边、副边端口接入线路投运时发生故障，则先依次分断CB1、CB6，将第一牵引变压器T 1退出运行，随后依次闭合CB2、CB7，将第二牵引变压器T 2投入运行；若第二牵引变压器T 2或其原边、副边端口接入线路投运时发生故障，则先依次分断CB2、CB7，将第二牵引变压器T 2退出运行，随后依次闭合CB1、CB6，将第一牵引变压器T 1投入运行。
进一步地，牵引变压器T 1与T 2可采用并列运行方式，该方式下，贯通式同相牵引变电所正常运行时，第一牵引变压器T 1与第二牵引变压器T 2均投入运行，三相断路器CB1、CB2、CB6、CB7均闭合。若第一牵引变压器T 1或其原边、副边端口接入线路发生故障，则分断CB1、CB6，将第一牵引变压器T 1退出运行；若牵引变压器T 2或其原边、副边端口接入线路发生故障，则分断CB2、CB7，将第二牵引变压器T 2退出运行。本申请贯通式同相牵引变电所的一组SPC中k个4P-MMC平均分担牵引负荷功率，每个4P-MMC允许通过的额定牵引负荷功率容量为S/k。检测到SPC中第i个变流器4P-MMC i发生故障，应立即闭锁4P-MMC i中功率器件触发脉冲，将其中三相断路器TB i和单相断路器SB i断开，SPC剩余的k-1个4P-MMC平均分担牵引负荷功率；相应地，牵引变电所允许通过的牵引负荷额定功率容量减小为(k-1)S/k。贯通式同相牵引变电所一组SPC中最多不超过k-1个4P-MMC发生故障时，该牵引变电所仍在贯通式同相牵引供电系统中运行。贯通式同相牵引变电所一组SPC中k个4P-MMC发生故障，贯通式同相牵引变电所发生故障退出运行，贯通式同 相牵引供电系统剩余的M-1个牵引变电所重新分配通过各牵引变电所的功率容量，并不影响贯通式牵引供电系统正常运行；其中每个贯通式同相牵引变电所应具备一定的冗余功率容量。
特别地，本申请实施例中一种在SPC退出运行后仍具备供电能力的贯通式同相牵引变电所，如图9所示，该实施例中，贯通式同相牵引变电所应满足U l＝U o。若该实施例贯通式同相牵引变电所SPC故障整体退出运行，分断SPC各4P-MMC的三相断路器TB i和单相断路器SB i，随即闭合断路器CB8，即可由三相牵引变压器T 1或T 2副边b 1(b 2)端口或c 1(c 2)端口直接向牵引母线T-bus供电，以节省其他各贯通式同相牵引变电所的功率容量，同时应调整贯通式同相牵引供电系统中其余M-1个贯通式同相牵引变电所SPC输出电压跟踪该牵引变电所端口b 1(b 2)或c 1(c 2)电压。
以用于直接供电制式的贯通式同相牵引供电系统为例，说明本申请具体实施方式，系统简图见图3。本具体实施例中，贯通式同相牵引变电所数量M＝1，牵引变压器T 1和T 2均采用YNd型接线，静止功率转换器SPC配置输出单相变压器T o，一组SPC所包含的四端口模块化多电平变流器4P-MMC的数量k＝1。同步公共交流电网额定线电压有效值U L＝110kV，牵引变压器副边额定线电压有效值U l＝27.5kV，牵引变压器变比K T为：
K T＝U l/U L＝0.25       (21)
本具体实施例中，SPC输出端口电压u xa(t)的相角δ x＝π，4P-MMC 1各相调制度满足m＝m x＝0.9，SPC输出端口Xc端口电压有效值U x为：
Figure PCTCN2020102122-appb-000021
贯通式同相牵引变电所内母线T-bus与接触网电压U o＝27.5kV，输出变压器T o变比K o为：
K o＝U o/U x＝0.87       (23)
4P-MMC 1中A 1，B 1，C 1相中上、下桥臂电压交流分量有效值U m为：
Figure PCTCN2020102122-appb-000022
4P-MMC 1直流正极DC+与负极DC-之间的额定直流电压U d为：
Figure PCTCN2020102122-appb-000023
4P-MMC 1中X 1相上、下桥臂电压交流分量有效值U xo、交流分量相位角δ xo为：
Figure PCTCN2020102122-appb-000024
本具体实施例中，电压源子模块采用半桥子模块，模块额定直流电压U c＝1kV，则4P-MMC 1的A 1，B 1，C 1，X 1相上、下桥臂中电压源子模块的数量N A，N B，N C，N X应满足：
Figure PCTCN2020102122-appb-000025
取N A＝N B＝N C＝N X＝50。
贯通式同相牵引变电所额定牵引负荷视在容量为S＝40MVA，令贯通式同相牵引变电所输入近端端口功率因数角
Figure PCTCN2020102122-appb-000026
输出近端端口功率因数角
Figure PCTCN2020102122-appb-000027
则牵引变压器副边端口电流有效值I l与SPC输出端口电流有效值I x分别为：
Figure PCTCN2020102122-appb-000028
在该具体实施例中，系统关键参数见下表：
Figure PCTCN2020102122-appb-000029
在该具体实施例中，4P-MMC各桥臂最大耐压，电流有效值，电流峰值与容量见下表：
Figure PCTCN2020102122-appb-000030
Figure PCTCN2020102122-appb-000031
文献2所述五端口交-直-交型MMC，在相同工况下，各桥臂最大耐压，电流有效值，电流峰值与容量见下表：
Figure PCTCN2020102122-appb-000032
4P-MMC各桥臂容量(有效值)之和为188.8MVA，各桥臂容量(峰值)之和为326.4MVA；文献2所述五端口交-直-交型MMC各桥臂容量(有效值)之和为289.2MVA，各桥臂容量(峰值)之和为498.4MVA。与文献2所述五端口交-直-交型MMC相比，本申请提出的4P-MMC整体可降低35％的功率器件和电容成本。

Claims (8)

  1. 一种基于四端口模块化多电平变流器的贯通同相牵引供电系统，其特征在于，由若干个间隔设置的贯通式同相牵引变电所组成，各贯通式同相牵引变电所的电源侧接入同一同步公共交流电网，各贯通式同相牵引变电所的负荷侧牵引母线均接入接触网T，所有贯通式同相牵引变电所之间通过接触网T全部相互贯通；
    各贯通式同相牵引变电所包括第一牵引变压器T 1、第二牵引变压器T 2、若干开关以及具有三个输入端口Ac、Bc、Cc和一个输出端口Xc的静止功率转换器SPC；所述第一牵引变压器T 1和第二牵引变压器T 2均为三相变压器结构，所述第一牵引变压器T 1和第二牵引变压器T 2的各相原边端口分别通过三相断路器CB1、CB2接入同步公共交流电网的A、B、C三相，其中A相超前于B相120°、A相滞后于C相120°，所述第一牵引变压器T 1和第二牵引变压器T 2的各相副边端口分别通过三相断路器CB6、CB7均接入所述静止功率转换器SPC的三个输入端口Ac、Bc、Cc，该静止功率转换器的输出端口Xc接入牵引母线T-bus，牵引母线T-bus通过单相断路器CB3接入接触网T，铁轨通过回流线接入相应贯通式同相牵引变电所内集中接地端；所述贯通式同相牵引变电所内集中接地端与静止功率转换器SPC的一个输入端口相连接，且各个贯通式同相牵引变电所内集中接地端接入该所的静止功率转换器SPC的输入端口相序号均相同；所述静止功率转换器SPC由k个四端口模块化多电平变流器4P-MMC并联组成，各四端口模块化多电平变流器4P-MMC均分别包括A、B、C、X四相，每相由上、下桥臂串联组成，各相上桥臂正极端相互并联形成直流正极DC+，各相下桥臂负极端相互并联形成直流负极DC-，各相上桥臂的负极端和下桥臂的正极端相串联作为对应相的中点，各四端口模块化多电平变流器4P-MMC的A、B、C三相中点分别通过一三相断路器TB接入静止功率转换器SPC的对应输入端口Ac、Bc、Cc，各四端口模块化多电平变流器4P-MMC的X相中点分别通过单相断路器SB接入静止功率转换器SPC的输出端口Xc；
    所述第一牵引变压器T 1和第二牵引变压器T 2的各原边端口间的额定线电压有效值U L均相等、各线电压相角依次相差120°，各副边端口间的额定线电压有效值U l均相等、各线电压相角依次相差120°，第一牵引变压器T 1和第二牵引变压器T 2变比均为K T：
    K T＝U l/U L。
  2. 根据权利要求1所述的贯通同相牵引供电系统，其特征在于，各贯通式同相牵引变电所还均分别包括单相输出变压器T o，该单相输出变压器T o的原边绕组一端口P 1接入相应贯通式同相牵引变电所内静止功率转换器SPC的输出端口Xc，所述静止功率转换器SPC的任一输入端口经断路器CB4接入所述单相输出变压器T o的原边绕组另一端口P 0，且各贯通式同相牵引变电所内单相输出变压器T o原边绕组端口P 0接入的该所静止功率转换器SPC的 输入端口相序号均相同；所述单相输出变压器T o的副边绕组一端口S 1经单相断路器CB5接入牵引母线T-bus，另一端口S 0接入相应贯通式同相牵引变电所内集中接地端；
    所述单相输出变压器T o的副边额定电压与牵引母线T-bus额定电压相同，记有效值为U o，单相输出变压器T o的原边额定电压与对应静止功率转换器SPC输出端口Xc的端口电压相同，记有效值为U x，则单相输出变压器T o变比K o为：
    K o＝U o/U x。
  3. 根据权利要求1或2所述的贯通同相牵引供电系统，其特征在于，各四端口模块化多电平变流器4P-MMC的各相中，上、下桥臂结构相同，均分别由若干个电压源子模块以及一台滤波电抗器依次串联组成；上桥臂中，第一个电压源子模块的正极端和滤波电抗器的一端分别作为上桥臂的正极端和负极端；下桥臂中，滤波电抗器的一端和最后一个电压源子模块的负极端分别作为下桥臂的正极端和负极端。
  4. 根据权利要求3所述的贯通同相牵引供电系统，其特征在于，令所述接触网T的额定电压有效值为U o，所述贯通式同相牵引变电所接入同步公共交流电网的额定线电压有效值为U L，每个贯通式同相牵引变电所的牵引负荷额定视在容量和牵引负荷功率因数角分别为S和
    Figure PCTCN2020102122-appb-100001
    令贯通式同相牵引变电所注入同步公共交流电网端口为正序电流，其近端端口功率因数角记为
    Figure PCTCN2020102122-appb-100002
    功率因数角均以电压滞后于电流为正；令集中接地端接入静止功率转换器SPC的输入端口Ac，即输入端口Ac以及与其相连的牵引变压器的副边端口均为参考电位，则静止功率转换器SPC的主要电气量特征设置如下：
    静止功率转换器SPC输入端口Ac、Bc、Cc和输出端口Xc的电压，即各四端口模块化多电平变流器4P-MMC的A、B、C、X相的交流端口电压u aa(t)，u ba(t)，u ca(t)，u xa(t)分别表示为：
    Figure PCTCN2020102122-appb-100003
    式中，ω为同步公共交流电网的角频率，t为系统时间；U l为第一牵引变压器T 1、第二牵引变压器T 2各副边端口间的额定线电压有效值，U x为静止功率转换器SPC的输出端口Xc电压u xa的有效值，δ x为u xa(t)的电压相位角，以超前于参考电压相量
    Figure PCTCN2020102122-appb-100004
    为正；
    各四端口模块化多电平变流器4P-MMC中A、B、C相的上、下桥臂电压交流分量有效值U m为：
    Figure PCTCN2020102122-appb-100005
    各四端口模块化多电平变流器4P-MMC的直流正极DC+与直流负极DC-之间的额定直流电压U d为：
    Figure PCTCN2020102122-appb-100006
    式中，m为各四端口模块化多电平变流器4P-MMC的A、B、C三相调制度；
    各四端口模块化多电平变流器4P-MMC的X相中上、下桥臂电压交流分量有效值U xo、交流分量相位角δ xo分别为：
    Figure PCTCN2020102122-appb-100007
    各四端口模块化多电平变流器4P-MMC的X相制度m x为：
    Figure PCTCN2020102122-appb-100008
    各四端口模块化多电平变流器4P-MMC的A、B、C、X相上、下桥臂电压分别为：
    Figure PCTCN2020102122-appb-100009
    所述第一牵引变压器T 1或第二牵引变压器T 2的A、B、C相副边端口电流为正序对称电流，其有效值均为I l，第一牵引变压器T 1或第二牵引变压器T 2的X相副边端口电流的有效值为I x，分别满足：
    Figure PCTCN2020102122-appb-100010
    各四端口模块化多电平变流器4P-MMC中A、B、C、X相的交流端口电流i a(t)，i b(t)，i c(t)，i x(t)分别为：
    Figure PCTCN2020102122-appb-100011
    各四端口模块化多电平变流器4P-MMC中A、B、C、X相的上、下桥臂电流分别为：
    Figure PCTCN2020102122-appb-100012
    式中，I da、I db、I dc、I dx分别为A 1，B 1，C 1，X 1相桥臂电流的直流分量，应满足：
    Figure PCTCN2020102122-appb-100013
  5. 根据权利要求4所述的贯通同相牵引供电系统，其特征在于，所述u xa(t)的电压相位角δ x的取值为：
    Figure PCTCN2020102122-appb-100014
  6. 根据权利要求4所述的贯通同相牵引供电系统，其特征在于，所述电压源子模块均为单相电压源型变流器结构，各四端口模块化多电平变流器4P-MMC的A、B、C、X相的上、下桥臂中电压源子模块的数量N A，N B，N C，N X分别满足：
    Figure PCTCN2020102122-appb-100015
  7. 根据权利要求4所述的贯通同相牵引供电系统，其特征在于，所述静止功率转换器 SPC中k个四端口模块化多电平变流器4P-MMC规格相同，各四端口模块化多电平变流器4P-MMC中各相上、下桥臂电流表示为：
    Figure PCTCN2020102122-appb-100016
  8. 根据权利要求7所述的贯通同相牵引供电系统，其特征在于，所述静止功率转换器SPC中各四端口模块化多电平变流器4P-MMC的各相调制度均相等，即m＝m x。
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