阅读说明：本技术 牵引变流系统 (Traction converter system ) 是由 刘可安 梅文庆 南永辉 文宇良 廖武 石煜 张朝阳 刘华东 杜凯冰 赵岸峰 于 2019-08-27 设计创作，主要内容包括：本发明提供一种牵引变流系统,用于对从外部电网接收的原始多相交流电进行电能变换以向牵引电机供给目标交流电。牵引变流系统主要由积木式单元、开关柜、集中控制装置组成,其中每个积木式变流单元分别接收原始多相交流电,并对原始多相交流电进行电能变换,以使得多个积木式变流单元输出多组不同相位的交流电。根据目标交流电的电流等级和/或电压等级,选择性地通过开关柜和集中控制装置将牵引变流系统切换至并联模式或串联模式,在并联模式中,每组中的单相交流电并联输出至牵引电机的单相定子绕组,以提供目标交流电所需的大电流。在串联模式中,每组中的单相交流电串联输出至牵引电机的单相定子绕组,以提供目标交流电所需的大电压。(The invention provides a traction current transformation system which is used for converting electric energy of original multi-phase alternating current received from an external power grid so as to supply target alternating current to a traction motor. The traction converter system mainly comprises building block type units, a switch cabinet and a centralized control device, wherein each building block type converter unit respectively receives original multi-phase alternating current and converts the electric energy of the original multi-phase alternating current so that a plurality of building block type converter units output a plurality of groups of alternating currents with different phases. And selectively switching the traction converter system to a parallel mode or a series mode through the switch cabinet and the centralized control device according to the current level and/or the voltage level of the target alternating current, wherein in the parallel mode, the single-phase alternating current in each group is output to a single-phase stator winding of the traction motor in parallel to provide large current required by the target alternating current. In series mode, the single phase alternating current in each group is output in series to the single phase stator windings of the traction motor to provide the large voltage required for the target alternating current.)

1. A traction converter system for converting electrical energy of a raw multi-phase alternating current received from an external grid to supply a target alternating current to a traction motor,

the traction converter system comprises m building block type converter units, wherein m is more than or equal to 2 and is an integer, and

each building block type current transformation unit is provided with n pairs of single-phase output terminals corresponding to the number of phases of the target alternating current, n is more than or equal to 3 and is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and is

The m building block type current transformation units respectively receive the original multiphase alternating current and carry out electric energy conversion on the original multiphase alternating current, so that m ith-phase single-phase alternating currents are output by corresponding m ith-phase single-phase output terminals of the m building block type current transformation units in a one-to-one correspondence mode, wherein i is more than or equal to 1 and less than or equal to n, i is an integer, and:

the traction converter system also comprises a switch cabinet, the m building block converter units are electrically connected to the traction motor through the switch cabinet, and the connection relation of m multiplied by n pairs of single-phase output terminals of the m building block converter units is changed in the switch cabinet according to the current level and/or the voltage level of the target alternating current so as to selectively switch the traction converter system to a parallel mode or a series mode.

2. The traction converter system of claim 1,

in the parallel mode, causing the m ith alternating currents to be output in parallel to an ith phase stator winding of the traction motor to supply an ith phase alternating current of the target alternating current to the traction motor by interconnecting respective m positive side output terminals of the m ith pairs of single-phase output terminals and electrically interconnecting respective m negative side output terminals of the m ith pairs of single-phase output terminals;

in the series mode, the m building block type current transformation units are sequentially cascaded in a mode of connecting a negative end output terminal of an ith pair of single-phase output terminals of a kth building block type current transformation unit and a positive end output terminal of an ith pair of single-phase output terminals of a (k + 1) th building block type current transformation unit, the m ith alternating currents are serially output to an ith phase stator winding of the traction motor so as to supply ith phase alternating currents of the target alternating currents to the traction motor, wherein k is more than or equal to 1 and less than m, and k is an integer.

3. A traction converter system for converting electrical energy of a raw multi-phase alternating current received from an external grid to supply a target alternating current to a traction motor,

the traction converter system comprises m building block type converter units, wherein m is more than or equal to 2 and is an integer, and

each building block type current transformation unit is provided with n pairs of single-phase output terminals corresponding to the number of phases of the target alternating current, n is more than or equal to 3 and is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and is

The m building block type variable current units respectively receive the original multi-phase alternating current and convert the electric energy of the original multi-phase alternating current so that m ith pair of single-phase output terminals of the m building block type variable current units correspondingly output m ith single-phase alternating currents one by one, wherein i is more than or equal to 1 and less than or equal to n, i is an integer, m corresponding positive end output terminals of the m ith pair of single-phase output terminals are mutually connected and corresponding m negative end output terminals of the m ith pair of single-phase output terminals are mutually and electrically connected, and the m ith alternating currents are electrically connected in parallel and output to an ith stator winding of the traction motor so as to supply ith alternating current of the target alternating current to the traction motor.

4. A traction converter system for converting electrical energy of a raw multi-phase alternating current received from an external grid to supply a target alternating current to a traction motor,

the traction converter system comprises m building block type converter units, wherein m is more than or equal to 2 and is an integer, and

each building block type current transformation unit is provided with n pairs of single-phase output terminals corresponding to the number of phases of the target alternating current, n is more than or equal to 3 and is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and is

The m building block type current transformation units respectively receive the original multiphase alternating current and carry out electric energy transformation on the original multiphase alternating current, so that m ith pair of single-phase output terminals of the m building block type current transformation units correspondingly output m ith single-phase alternating currents in a one-to-one manner, wherein i is more than or equal to 1 and less than or equal to n, and i is an integer,

the m building block type current transformation units are sequentially cascaded in a mode of leading a negative end output terminal of an ith pair of single-phase output terminals of a kth building block type current transformation unit and a positive end output terminal of an ith pair of single-phase output terminals of a (k + 1) th building block type current transformation unit, the m ith alternating currents are serially connected and output to an ith phase stator winding of the traction motor, so that the ith phase alternating current of the target alternating current is supplied to the traction motor, wherein k is more than or equal to 1 and is less than m, and k is an integer.

5. The traction conversion system according to any one of claims 1 to 4, wherein:

each building block type current transformation unit comprises a transformer unit and n current transformation subunits, wherein

The transformer unit is used for phase-shifting and reducing the original multi-phase alternating current into n low-voltage multi-phase alternating currents to be respectively supplied to the n converter subunits,

in the n converter subunits, the ith converter subunit converts the ith low-voltage multi-phase alternating current into the ith single-phase alternating current.

6. The traction conversion system according to any one of claims 1 to 4, wherein:

the original multi-phase alternating current and the target alternating current are both three-phase alternating currents.

7. The traction conversion system according to claims 1-4, wherein:

the switch cabinet comprises 2 x m x n controllable switches, and one end of each controllable switch is connected with m x n pairs of single-phase output terminals of the m building block type converter units in a one-to-one correspondence manner;

and selectively switching the traction current transformation system to the parallel mode or the series mode by changing the connection relation of the other ends of the 2 Xm Xn controllable switches.

8. The traction converter system of claim 5, wherein:

the converter sub-unit is a multi-level converter unit which comprises a multi-phase rectification power unit, a single-phase inversion unit, a capacitor unit and an output reactance unit.

9. The traction conversion system according to any one of claims 1 to 4, wherein:

the number of the building block type current transformation units can be changed according to the voltage level and/or the current level of the target alternating current.

10. The traction conversion system according to any one of claims 1 to 4, wherein:

the traction converter system comprises two building block type converter units.

Technical Field

The invention relates to a traction converter system of a rail transit traction power supply system, in particular to a building block type traction converter for rail transit.

Background

Different from the traditional train transmission system, the medium-high speed magnetic suspension traffic generally adopts a long stator linear synchronous motor, the stator core of the long stator linear synchronous motor is continuously laid below the two sides of a magnetic suspension track, the stator winding of the long stator linear synchronous motor is embedded in the stator core slot, and the excitation winding is assembled on the train. A high-power converter arranged on the ground is used for supplying power to a stator winding of the long-stator linear synchronous motor, and a vehicle-mounted generator and a battery are used for supplying power to an excitation winding and a suspension system.

The high-speed magnetic suspension transmission has the characteristics of wide speed regulation range, low-speed large current, high speed and high voltage, so the scheme of the converter is always more complex. The scheme that siemens adopts at present in the Shanghai is that input voltage ware + GTO medium voltage converter + output transformer, adopts two sets of ground converters to pass through bi-polar power supply when needing bigger power.

The main problems with this solution are: (1) since the output transformer has a wide operating range, its design and manufacturing process are complicated. (2) The transformer is not a standardized product, and the speed of the line needs to be increased later, so that the voltage and current requirements may not be met or a large margin needs to be reserved for the initial design.

Therefore, the traditional rail transit converter main circuit scheme is complex, and the problems that the type selection of the transformer is difficult, the capacity expansion is difficult and the like exist.

Disclosure of Invention

Aiming at the problems, the invention provides a traction current transformation system using a building block type current transformation unit.

The invention provides a traction converter system, which carries out electric energy conversion on original multi-phase alternating current received from an external power grid so as to supply target alternating current to a traction motor, and comprises m building block type converter units, wherein m is more than or equal to 2 and m is an integer, each building block type converter unit is respectively provided with n pairs of single-phase output terminals corresponding to the phase number of the target alternating current, n is more than or equal to 3 and n is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and the m building block type current transformation units respectively receive the original multiphase alternating current and carry out electric energy conversion on the original multiphase alternating current, so that m ith pair of single-phase output terminals of the m building block type current transformation units correspondingly output m ith single-phase alternating currents one by one, wherein i is more than or equal to 1 and less than or equal to n, i is an integer, and: the traction converter system also comprises a switch cabinet, wherein the m building block converter units are electrically connected to the traction motor through the switch cabinet, and the connection relation of m multiplied by n pairs of single-phase output terminals of the m building block converter units in the switch cabinet is changed according to the current level and/or the voltage level of the target alternating current so as to selectively switch the traction converter system to a parallel mode or a series mode.

Preferably, in the parallel mode, the m ith alternating currents are output in parallel to the ith-phase stator winding of the traction motor by interconnecting respective m positive-end output terminals of the m ith pairs of single-phase output terminals and electrically interconnecting respective m negative-end output terminals of the m ith pairs of single-phase output terminals to supply the ith phase alternating current of the target alternating current to the traction motor; in the series mode, the m building block type current transformation units are sequentially cascaded in a mode of connecting a negative end output terminal of the ith pair of single-phase output terminals of the kth building block type current transformation unit with a positive end output terminal of the ith pair of single-phase output terminals of the kth building block type current transformation unit, the m ith alternating current is output to the ith phase stator winding of the traction motor in series so as to supply the ith phase alternating current of the target alternating current to the traction motor, wherein k is more than or equal to 1 and less than m, and k is an integer.

The invention provides a traction converter system, which carries out electric energy conversion on original multi-phase alternating current received from an external power grid so as to supply target alternating current to a traction motor, and comprises m building block converter units, wherein m is more than or equal to 2 and m is an integer, each building block converter unit is respectively provided with n pairs of single-phase output terminals corresponding to the phase number of the target alternating current, n is more than or equal to 3 and n is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and the m building block type variable current units respectively receive the original multi-phase alternating current and convert the electric energy of the original multi-phase alternating current so as to enable corresponding m ith pairs of single-phase output terminals of the m building block type variable current units to correspondingly output m ith single-phase alternating currents one by one, wherein i is more than or equal to 1 and less than or equal to n, i is an integer, corresponding m positive end output terminals of the m ith pairs of single-phase output terminals are mutually connected and corresponding m negative end output terminals of the m ith pairs of single-phase output terminals are mutually and electrically connected, and the m ith electric alternating currents are parallelly output to an ith stator winding of the traction motor so as to supply the ith alternating current of the target alternating current to the traction motor.

The third aspect of the invention provides a traction converter system, which performs electric energy conversion on original multi-phase alternating current received from an external power grid to supply target alternating current to a traction motor, and comprises m building block converter units, wherein m is more than or equal to 2 and m is an integer, each building block converter unit is respectively provided with n pairs of single-phase output terminals corresponding to the phase number of the target alternating current, n is more than or equal to 3 and n is an integer, and each pair of single-phase output terminals respectively comprises a positive end output terminal and a negative end output terminal; and the m building block type current transformation units respectively receive the original multi-phase alternating current and perform electric energy conversion on the original multi-phase alternating current so as to enable corresponding m ith pair of single-phase output terminals of the m building block type current transformation units to correspondingly output m ith phase single-phase alternating currents one by one, wherein i is more than or equal to 1 and less than or equal to n and i is an integer, the m building block type current transformation units are sequentially cascaded in a mode of connecting a negative end output terminal of the ith pair of single-phase output terminals of the kth building block type current transformation unit with a positive end output terminal of the ith pair of single-phase output terminals of the kth building block type current transformation unit, the m ith alternating currents are serially connected to an ith phase stator winding of the traction motor so as to supply the ith phase alternating current of the target alternating current to the traction motor, and k is more than or equal to 1 and less than or equal to m and k is an integer.

Preferably, each of the building block type converter units includes a transformer unit and n converter subunits, wherein the transformer unit is configured to phase-shift and step-down the original multi-phase ac power into n low-voltage multi-phase ac powers to be supplied to the n converter subunits, respectively, and in the n converter subunits, an ith converter subunit converts an ith low-voltage multi-phase ac power into an ith phase single-phase ac power.

Preferably, the original multi-phase alternating current and the target alternating current are both three-phase alternating currents.

Preferably, the switch cabinet comprises 2 × m × n controllable switches, and one end of each controllable switch is connected to m × n pairs of single-phase output terminals of the m building block converter units in a one-to-one correspondence manner; and selectively switching the traction current-converting system to the parallel mode or the series mode by changing the connection relation of the other ends of the 2 Xm Xn controllable switches.

Preferably, the converter subunit is a multi-level converter unit, and the multi-level converter unit includes a multiphase rectification power unit, a single-phase inverter unit, a capacitor unit and an output reactance unit.

Preferably, the number of the building-block type current transformation units can be changed according to the voltage level and/or the current level of the target alternating current.

Preferably, the traction converter system comprises two building block converter units.

By using the traction current transformation system, when low-voltage large current is needed, a plurality of building block type current transformation units are connected in parallel for output, and when high-voltage small current is needed, a plurality of building block type current transformation units are connected in series for output.

The advantages are that:

(1) the building block type structure can be set to be connected with large current in parallel or connected with high voltage in series according to requirements;

(2) the cost of spare parts is reduced;

(3) when a line is transformed or the speed is increased, the capacity of the converter is easy to expand.

Drawings

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. It is to be noted that the appended drawings are intended as examples of the claimed invention. In the drawings, like reference characters designate the same or similar elements.

Fig. 1 shows a system composition schematic of the traction converter system of the present invention.

Fig. 2 shows a schematic composition diagram of a building block type converter unit of the traction converter system.

Fig. 3 shows a schematic diagram of an input phase shifting transformer as an example of a transformer unit of the traction converter system of the present invention.

Fig. 4 shows a schematic diagram of a three-level converter subunit as an example of a converter subunit of the traction converter system of the present invention.

Fig. 5 shows a schematic diagram of the system components when operating in series mode as the traction converter system of the present invention.

Fig. 6 shows a schematic diagram of the system components when operating in parallel mode as a traction converter system of the present invention.

Fig. 7 shows a schematic composition diagram of the traction converter system of the present invention with more than two building block converter units.

Detailed Description

The detailed features and advantages of the present invention are described in detail in the detailed description which follows, and will be sufficient for anyone skilled in the art to understand the technical content of the present invention and to implement the present invention, and the related objects and advantages of the present invention will be easily understood by those skilled in the art from the description, claims and drawings disclosed in the present specification.

Fig. 1 shows a traction converter system 1 of the invention, the traction converter system 1 performing an electrical energy conversion of the original multi-phase alternating current received from the external grid to supply the target alternating current to the traction motor LSM. The traction converter system 1 of the present invention is described herein with an example of powering a high speed maglev traction motor, i.e., the original multi-phase alternating current and the target alternating current are both three-phase alternating current.

The traction converter system 1 comprises a building block type converter unit module 10, a switch cabinet 20 and a centralized control device 30.

Building block type unit

The building block type current transformation unit module 10 may include two building block type current transformation units M1 and M2 as shown in fig. 1, or may include more than two building block type current transformation units M1 as shown in fig. 7, where M2, … … Mj is an integer greater than 2. The modular converter unit module 10 of the present invention is illustrated in fig. 2, and each modular converter unit has three pairs of single-phase output terminals corresponding to the number of phases (i.e., three phases) of the target ac power. The three pairs of single-phase output terminals include a pair of a-phase output terminals, a pair of B-phase output terminals, and a pair of C-phase output terminals. Here, each pair of single-phase output terminals includes a positive output terminal and a negative output terminal, respectively.

When the alternating current with more phases is output, the single-phase output terminal pairs of each building block type current transformation unit are correspondingly increased.

Here, the target alternating current is exemplarily made to be three-phase alternating current, and then a pair of phase a output terminals of the building block type current transformation unit M1 respectively have a positive output terminal M1A + and a negative output terminal M1A —; the phase B output terminals respectively have a positive output terminal M1B + and a negative output terminal M1B-, and so on for phase C. The cordwood converter unit M2 has the same structure as the cordwood converter unit M1, namely, a pair of A-phase output terminals of the cordwood converter unit M2 respectively have a positive output terminal M2A + and a negative output terminal M2A-, and the B-phase and the C-phase and the like.

The two building block type current transformation units M1 and M2 respectively receive the same original three-phase alternating current U, V, W and perform electric energy conversion on the original three-phase alternating current, so that the corresponding two ith-phase output terminals of the two building block type current transformation units M1 and M2 correspondingly output two ith-phase single-phase alternating currents with controlled output amplitude and phase according to the setting of the centralized control device 30, wherein i is more than or equal to 1 and less than or equal to 3.

For example, the first A-phase alternating current is output between a pair of A-phase output terminals M1A + and M1A-of the building block type current transformation unit M1. A second A-phase alternating current is output between a pair of A-phase output terminals M2A + and M2A-of the building block type current transformation unit M2. It is obvious that the number of single-phase ac currents corresponds to the number of modular converters.

Similarly, the two building block type current transformation units M1 and M2 also output two B-phase alternating currents and two C-phase alternating currents. For a conventional three-phase system, the fundamental voltage phases of the a, B and C phases are sequentially staggered by 120 degrees.

Fig. 2 to 4 specifically show a specific structure of a building block converter unit M1 of the present invention, and here, the way in which the building block converter unit of the present invention implements the above-mentioned three-phase input-three-phase output converter function is described with reference to fig. 2 to 4.

Each modular converter unit comprises a single multi-winding transformer unit 11, three converter subunits 12A, 12B, 12C and a control subunit 13.

Multi-winding transformer

The multi-winding transformer unit 11 is responsible for converting a grid-side high voltage (e.g. 10Kv or 35Kv) into an isolated low voltage (e.g. 3Kv), and is schematically shown in fig. 3, specifically, the multi-winding transformer unit 11 is used for shifting and stepping down an original three-phase alternating current into three low-voltage three-phase alternating currents, which are respectively supplied to three-level converter sub-units 12A, 12B, and 12C.

That is, a set of three output low-voltage terminals TA1, TB1, TC1 of multi-winding transformer unit 11 are connected to three-phase input terminals LA1, L1B, LC1 of converter sub-unit 12A, respectively, to supply low-voltage three-phase alternating current to converter sub-unit 12A. Another set of three output low voltage terminals TA2, TB2, TC2 are connected to three-phase input terminals LA2, LB2, LC2 of inverter subunit 12B, respectively, to supply low voltage three-phase alternating current to inverter subunit 12B.

In each building block type current transformation unit, the number of current transformation subunits and the number of low-voltage multi-phase alternating current converted by the multi-winding transformer also correspond to the number of phases of target alternating current, namely the number of pairs of single-phase output terminals. Here, since the target alternating current is a three-phase alternating current, the multi-winding transformer unit converts the original three-phase alternating current into three low-voltage three-phase alternating currents.

Thus, a set of low-voltage multi-phase alternating currents has been obtained, the number of phases and number of phases corresponding to the number of converter subunits.

Converter unit

Next, as shown in fig. 2, an intermediate conversion process of multi-phase input to single-phase output is performed.

The ith converter subunit in the three converter subunits 12A, 12B and 12C converts the ith low-voltage multi-phase alternating current into the ith phase single-phase alternating current, so that the phase number is 3, and i is more than or equal to 1 and less than or equal to 3.

In other words, the first converter subunit 12A converts the low-voltage three-phase ac power, obtained by phase-shifting and voltage-reducing the multi-winding transformer unit 11, into a first-phase single-phase ac power, for example, an a-phase ac power, and outputs the first-phase single-phase ac power through the pair of a-phase output terminals M1A + and M1A-of the building block converter unit M1.

The second converter sub-unit 12B converts the low-voltage three-phase ac power obtained by phase-shifting and voltage-reducing the first ac power through the multi-winding transformer unit 11 into a second-phase single-phase ac power, such as a B-phase ac power, and outputs the second-phase single-phase ac power through a pair of B-phase output terminals M1B + and M1B-of the building block converter unit M1.

Similarly, the third converter subunit 12C converts and generates C-phase alternating current, and outputs the C-phase alternating current through C-phase output terminals M1C +, M1C-.

Specifically, taking the first converter subunit 12A as an example, fig. 4 shows a three-level converter unit employed in the present invention, and the remaining two converter subunits 12B and 12C can have the same structure as the first converter subunit.

In the first converter subunit 12A, a three-phase rectification power unit 12A1, a single-phase inversion unit 12A2, a capacitor unit 12A3 and an output reactance 12A4 unit are included. Under the control of the control subunit 13, the three-phase rectification power unit 12a1 and the single-phase inversion unit 12a2 become a single-phase ac output, such as an a ac output, through three-phase controllable rectification and single-phase inversion.

Here, the converter subunits 12A, 12B, and 12C are three-level converter units. That is, if the total dc voltage is Ud, the phase voltages can output three voltage levels of +0.5Ud, 0 and-0.5 Ud, and one converter subunit line voltage can output five voltage levels of + Ud, +0.5Ud, 0 and-0.5 Ud and Ud. The converter subunit may also adopt other multi-level converter units in the prior art, such as a five-level converter unit, a seven-level converter unit, an MMC converter unit in any combination, and the like. The power cells may be comprised of IGBTs, IEGTs, or IGBTs.

Control subunit

The control subunit 13 mainly includes a control board, an optical fiber, a drive board, a voltage sensor, a current sensor, and the like, and receives and analyzes a command from the centralized control device 30 (see fig. 1) to be converted into pulse trigger control for the switching devices of the three-phase rectification power unit 12a1 and the single-phase inversion unit 12a 2.

Fig. 5 and 6 are schematic diagrams of two building block type current transforming units realizing high voltage/large current through series/parallel combination, while three current transforming subunit 12A, 12B, 12C of M1 respectively output a-phase alternating current, B-phase alternating current and C-phase alternating current through a-phase output terminal M1A +, M1A-, B-phase output terminal M1B +, M1B-and C-phase output terminal M1C +, M1C-respectively, the building block type current transforming unit M2 also respectively outputs a-phase alternating current, B-phase alternating current and C-phase alternating current through a-phase output terminal M2A +, M2A-, B-phase output terminal M2B +, M2B-and C-phase output terminal M2C +, M2C-respectively in the same way as the building block type current transforming unit M1, as shown in fig. 5 and 6.

Therefore, compared with the traditional circuit structure, the traction power supply system of the invention omits an output transformer, and independently sets a phase-shifting step-down transformer (namely, a multi-winding transformer 11) for each building block type current transformation unit. Therefore, when capacity expansion is needed, only the number of the building block type current transformation units is needed to be increased, and the input transformer is not needed to be modified like the prior art, namely, the number of the building block type current transformation units and the series-parallel combination can be changed according to the voltage grade and/or the current grade of the target alternating current according to the application system requirement. For example, the traction converter system 1 shown here includes two building block converter units M1, M2, but when the converter needs to be expanded, there may be any number of building block converter units, which is simple and convenient, and has strong adaptability, as shown in fig. 7.

Switch cabinet

As shown in fig. 1, 5 and 6, the traction converter system 1 further includes a switch cabinet 20, two building block converter units M1, M2 are electrically connected to the traction motor LSM through the switch cabinet 20, and: the switch cabinet 20 includes a series of controllable switches J1-J12, one end of each controllable switch is connected to six pairs of single-phase output terminals of two building block converter units M1 and M2 in a one-to-one correspondence, that is, the number of controllable switches is twice the product of the number of building block converter units and the target ac phase number, for example, two building block units in a three-phase system shown in the figure have 2 × 3 × 2 to 12 controllable switches J1-J12. And selectively switching the traction converter system 1 to a parallel mode or a series mode by changing the connection relation of the other ends of the twelve controllable switches. More switches are needed if more building elements are used.

Specifically, according to the current level and/or the voltage level of the target alternating current, the connection relationship of twelve single-phase output terminals of two or more building block type converter units in the switch cabinet 20 is changed, that is, the connection relationship of the other ends of twelve controllable switches connected in one-to-one correspondence with the twelve single-phase output terminals is changed, so that the traction converter system is selectively switched to the parallel mode or the series mode.

The series mode and the parallel mode of the traction converter system of the present invention will be described separately below.

Series mode

Referring to FIG. 5, taking two building block type current transformation units as an example (M1, M2), the i-th pair of single-phase negative output terminals of M1 are connected with the corresponding positive output terminal of M2, the positive output terminal of M1 is connected to the stator of the motor, and the negative terminals of M2 are connected backwards in sequence, so that the number of phases is 3, and therefore, i is more than or equal to 1 and less than or equal to 3.

That is, the other end of the controllable switch J1 connected to the positive output terminal M1A + among the a-phase output terminals in the building block converter unit M1 is connected to the a-phase stator winding of the traction motor LSM, the other end of the controllable switch J2 connected to the negative output terminal M1A-among the a-phase output terminals in the building block converter unit M1 and the other end of the controllable switch J7 connected to the positive output terminal M2A + among the a-phase output terminals in the building block converter unit M2 are connected, and the other end of the controllable switch J8 connected to the a-phase negative output terminal M2A-among the building block converter unit M2 is connected to the neutral point U0, so that two a-phase alternating currents are output in series to the a-phase stator winding of the traction motor to supply the a-phase alternating current of the target three-phase alternating current to the traction motor.

By analogy, the controllable switch J3 is connected to the B-phase stator winding of the traction motor LSM, the controllable switch J4 is connected to the controllable switch J9, and the controllable switch J10 is connected to the neutral point U0, so that two B-phase alternating currents are output in series to the B-phase stator winding of the traction motor to supply the B-phase alternating currents of the target three-phase alternating currents to the traction motor.

The controllable switch J5 is connected to the C-phase stator winding of the traction motor LSM, the controllable switch J6 is connected to the controllable switch J11, and the controllable switch J12 is connected to the neutral point U0, so that two C-phase alternating currents are output in series to the C-phase stator winding of the traction motor to supply the C-phase alternating current of the target three-phase alternating current to the traction motor.

Parallel mode

Referring to FIG. 6, the positive output terminals of the i-th pair of single-phase output terminals of each of the two modular converter units M1, M2 are connected to each other and the negative output terminals are also connected to each other, so that the number of phases is 3, and thus 1 ≦ i ≦ 3. That is, the other end of the controllable switch J1 connected to the positive output terminal M1A + among the a-phase output terminals in the block converter unit M1 and the other end of the controllable switch J7 connected to the positive output terminal M2A + among the a-phase output terminals in the block converter unit M2 are connected to each other and to the a-phase stator winding of the traction motor LSM as the motor stator a-phase, the controllable switch J3 and the controllable switch J6 are connected to each other and to the B-phase stator winding of the traction motor LSM as the motor stator B-phase, the controllable switch J5 and the controllable switch J11 are connected to each other and to the C-phase stator winding of the traction motor LSM as the motor stator C-phase, and all controllable switches J2, J4, J6, J8, J10, J12 connected to the negative side output terminals M1A-, M1B-, M1C-, M2A-, M2B-, M2C-are connected to the neutral point U0.

In this way, the two a-phase alternating currents of the two building block type current converting units M1 and M2 are output to the a-phase stator winding of the traction motor in parallel, the two B-phase alternating currents of the two building block type current converting units M1 and M2 are output to the B-phase stator winding of the traction motor in parallel, and the two C-phase alternating currents of the two building block type current converting units M1 and M2 are output to the C-phase stator winding of the traction motor in parallel, so as to supply the a-phase alternating current, the B-phase alternating current and the C-phase alternating current of the target three-phase alternating current to the traction motor respectively.

In other words, since the m building block converter units all generate the same number of single-phase alternating currents as the target alternating current phase number n, the total number of all the single-phase alternating currents is the product m × n of the number of building block converter units and the target alternating current phase number. By grouping the m × n single-phase alternating currents by phase, the single-phase alternating currents of m same phases in each group are selectively connected in series or in parallel. Even under the condition that the number of the building block type current transformation units is determined, the total output voltage and the total output current of the whole traction current transformation system 1 can be changed, high voltage is realized through the series combination of the building block type current transformation units and the switches, high current output is realized through the parallel combination, and high voltage and high current are realized through mixed output so as to adapt to the current grade and/or voltage grade change of target alternating current.

Centralized control device 30

The centralized control device 30 in fig. 1 is an overall control unit of the entire converter system, performs data interaction with a control subunit of the building block converter unit module 10 through optical fibers, mainly collects information such as voltage, current, power device state and the like of the converter subunit in the building block converter unit module 10, and controls the on and off of the power device through optical fiber transmission trigger pulses to control the phase of the output voltage of the building block converter unit module 10. The centralized control also collects the states of the switches and the voltage and current information of the load in the switch cabinet 20, and issues different commands to control the on and off of the switches of the switch cabinet according to the needs of different occasions.

The terms and expressions which have been employed herein are used as terms of description and not of limitation. The use of such terms and expressions is not intended to exclude any equivalents of the features shown and described (or portions thereof), and it is recognized that various modifications may be made within the scope of the claims. Other modifications, variations, and alternatives are also possible. Accordingly, the claims should be looked to in order to cover all such equivalents.

Certain terms are used throughout this specification to refer to particular system components. As one skilled in the art will appreciate, identical components may generally be referred to by different names, and thus this document does not intend to distinguish between components that differ in name but not function. In this document, the terms "including", "comprising" and "having" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to …".

Also, it should be noted that although the present invention has been described with reference to the current specific embodiments, it should be understood by those skilled in the art that the above embodiments are merely illustrative of the present invention, and various equivalent changes or substitutions may be made without departing from the spirit of the present invention, and therefore, it is intended that all changes and modifications to the above embodiments be included within the scope of the claims of the present application.