A structure for converting a traction transformer with Vx wiring into flexible single-phase wiring

Abstract

The application provides a structure for converting a Vx wiring traction transformer into a flexible single-phase wiring, which is based on two single-phase transformers and a same-phase power supply device, a1x1 winding and a2x2 winding on the secondary side of transformer A are connected in parallel to form parallel winding 1; b1y1 winding and b2y2 winding on the secondary side of transformer B are connected in parallel to form parallel winding 2; the parallel winding 2 and the same-phase power supply device are connected in parallel to form parallel same-phase winding; the parallel winding 1 and the parallel same-phase winding are connected in series, the series connection point is grounded, and the non-series connection points are respectively connected with a catenary and a positive feeder to form a 2*27.5kV power supply structure. The application realizes the flexible single-phase wiring reconstruction of a three-phase Vx wiring traction substation, can utilize the existing three-phase Vx wiring traction transformer, avoids the related reconstruction and abandoned project caused by replacing the traction transformer, avoids the high-voltage side reconstruction, reduces the influence on the normal operation organization of the railway during the reconstruction, and can save the cost of re-evaluating the power quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of traction power supply system, in particular to a structure for converting a Vx wiring traction transformer into a flexible single-phase wiring. BACKGROUND

[0002] The three-phase Vx wiring traction transformer is a transformer used for AT power supply mode of electrified railway, which is usually composed of two single-phase transformers for AT power supply, and the two single-phase transformers supply power to two power supply arms of a traction substation respectively. Each single-phase transformer is a 3-winding transformer, and each phase has two secondary windings, and the two secondary windings output ±27.5kV respectively, and the winding neutral point is grounded.

[0003] Compared with the Scott wiring traction transformer, the three-phase Vx wiring traction transformer can save the outlet autotransformer (AT), and compared with the cross wiring traction transformer, the capacity utilization rate of the transformer is higher. The maturity of this wiring type has been recognized by the industry, and it has been widely used in projects using AT power supply mode in the field of high-speed railway and heavy haul railway.

[0004] The same phase power supply, i.e. the same phase power supply technology, refers to a traction power supply mode in which the section of the catenary voltage phase of adjacent substations on the line is the same, and there is no electric phase splitting link on the line. In theory, the same phase power supply can be realized by using single-phase transformers in all traction substations, but due to the single-phase load causing negative sequence current in the power system, when the power system is weak, it will cause serious three-phase imbalance, so the power department will not agree to use single-phase transformers. Therefore, the key technology of the same phase power supply is to realize three-phase and single-phase symmetric transformation in the traction substation, and to use the same phase power supply device.

[0005] Most of the main lines of existing high-speed railways or heavy haul railways use AT power supply mode, and the traction substations mostly use three-phase Vx wiring type. If flexible single-phase wiring reconstruction is carried out, two methods are generally used: one is to directly replace the balanced wiring type traction transformer, and the other is to adjust the wiring type of the high voltage side of the traction transformer, and adjust the connection of one traction transformer to the middle end of the high voltage side of another traction transformer. However, the above two reconstruction methods face the following problems in actual operation, one is that the balanced wiring type traction transformer directly replaced needs to replace two Vx wiring transformers to bear the load of the entire traction substation, and the transformer capacity is large, and a large amount of civil construction reconstruction of the original traction substation is required, and the other is that the high voltage side wiring adjustment of the traction transformer needs to be evaluated and approved by the power grid department.

[0006] In the prior art, the traction substation with flexible single-phase connection mostly adopts the traction transformer with unequal capacity balance connection type. If the traction substation with existing three-phase Vx connection is directly transformed into the same-phase power supply by using the traction transformer with unequal capacity balance connection type, the existing traction transformer will be discarded, the civil construction will be reconstructed, the high-voltage side of the traction transformer will be reconstructed, and the like, which is not conducive to the popularization and application of the same-phase power supply technology in the field of high-speed railway and heavy haul railway with a large number of traction transformers with three-phase Vx connection type. SUMMARY

[0007] Therefore, the present application aims to provide a structure for converting a Vx connection traction transformer into a flexible single-phase connection, so as to solve the problems of traction transformer discarding, large-scale civil construction, high-voltage side connection reconstruction, and the like caused by the reconstruction of the traction substation with existing three-phase Vx connection into flexible single-phase connection.

[0008] In a first aspect, the present application provides a structure for converting a Vx connection traction transformer into a flexible single-phase connection, based on two single-phase transformers and a same-phase power supply device, comprising,

[0009] a1x1 winding and a2x2 winding on the secondary side of transformer A are connected in parallel to form parallel winding 1;

[0010] b1y1 winding and b2y2 winding on the secondary side of transformer B are connected in parallel to form parallel winding 2;

[0011] the parallel winding 2 and the same-phase power supply device are connected in parallel to form parallel same-phase winding;

[0012] the parallel winding 1 and the parallel same-phase winding are connected in series, the series connection point is grounded, and the non-series connection points are respectively connected to the overhead contact line and the positive feeder to form a 2×27.5kV power supply architecture.

[0013] Preferably, the phase of the parallel winding 1 is consistent with the AB phase of the primary side of the same-phase transformer A, and the phase of the parallel same-phase winding is 180° out of phase after the CB phase of the primary side of the same-phase transformer B is phase-shifted by the same-phase power supply device.

[0014] Preferably, the same-phase power supply device comprises a step-down transformer, an AC-DC-AC conversion device and a matching transformer connected in sequence, for phase-shifting the input voltage of the parallel winding 2 by 120° and outputting a voltage with a phase difference of 180° from the parallel winding 1.

[0015] Preferably, the AC-DC-AC conversion device adopts a three-level NPC topology structure, and realizes dynamic phase adjustment through SPWM modulation, with an adjustment range of ±5°.

[0016] A same-phase power supply device comprises:

[0017] Step-down transformer, input side connected with parallel winding 2, output side connected with AC-DC-AC conversion device;

[0018] AC-DC-AC conversion device, containing rectifier, DC bus and inverter, used for realizing 120° basic phase offset;

[0019] Matching transformer, input side connected with inverter output, output side generating z1c1 winding.

[0020] Preferably, the AC-DC-AC conversion device is configured with a harmonic suppression module, and the total harmonic distortion rate of the output is less than 3%.

[0021] A flexible single-phase wiring structure, comprising: the primary side of transformer A and transformer B is connected to the AB phase and CB phase of the three-phase power grid respectively; the secondary side forms a 2*27.5kV output through parallel-serial reconstruction and same-phase power supply device, and the neutral point is grounded through a non-linear resistor.

[0022] The embodiment of the present application brings the following beneficial effects:

[0023] The present application realizes the flexible single-phase wiring reconstruction of the traction substation of the three-phase Vx wiring, can realize the utilization of the existing three-phase Vx wiring traction transformer, avoids the related reconstruction and abandoned engineering caused by replacing the traction transformer, avoids the high-voltage side reconstruction, reduces the influence on the normal operation organization of the railway during the reconstruction. At the same time, the cost of re-evaluating the power quality can be saved.

[0024] Other features and advantages of the present application will be described in the following specification, and some features will become apparent from the specification, or will be understood by those skilled in the art through implementation of the present application. The purpose and other advantages of the present application are realized and obtained by the structure specifically pointed out in the specification, claims and drawings.

[0025] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a terminal connection schematic diagram of the three-phase Vx wiring type in the prior art;

[0027] Figure 2 It is a phase angle schematic diagram of the three-phase Vx wiring type in the prior art;

[0028] Figure 3 It is a schematic diagram of converting the Vx wiring traction transformer into a flexible single-phase wiring scheme according to the embodiment of the present application;

[0029] Figure 4 It is a terminal connection schematic diagram of converting the Vx wiring traction transformer into a flexible single-phase wiring according to the embodiment of the present application;

[0030] Figure 5 The phase angle diagram of the Vx connection traction transformer is converted to flexible single-phase connection for the embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0032] Referring to Figure 1 and Figure 2 , the structure of the Vx connection traction transformer in the existing high-speed railway and heavy-haul railway is composed of two single-phase transformers to form a three-phase Vx connection structure, and the three-phase Vx connection case and the three-phase Vx connection phase angle case are as follows.

[0033] The three-phase Vx connection case is that one single-phase transformer high-voltage side is connected to the A and B phases of external power, the a1x1 winding and the a2x2 winding of the secondary side are connected in series, the series connection point of the two windings is connected to the ground R, and the non-series connection points of the two windings are respectively supplied with power by the catenary T and the positive feeder F, that is, the x1 terminal and the a2 terminal are connected and then grounded, the a1 terminal is connected to the catenary T, and the x2 terminal is connected to the positive feeder F.

[0034] The three-phase Vx connection phase angle case is that the phase angle between the original side AB phase and the CB phase is 60 degrees; the secondary side winding a1- (a2, x1) -x2 is consistent with the AB phase, wherein the a2 terminal and the x1 terminal are grounded, the phase difference between the a1 terminal and the x2 terminal is 180 degrees, and the phase difference corresponds to 27.5 kV and -27.5 kV respectively, and the a1 terminal and the x2 terminal are respectively supplied with power by the catenary T and the positive feeder F; the secondary side winding y2- (b2, y1) -b1 is consistent with the CB phase, wherein the b2 terminal and the y1 terminal are grounded, the phase difference between the y2 terminal and the b1 terminal is 180 degrees, and the phase difference corresponds to 27.5 kV and -27.5 kV respectively, and the y2 terminal and the b1 terminal are respectively supplied with power by the catenary T and the F bus.

[0035] Referring to Figure 3The structure for converting a Vx-connected traction transformer to a flexible single-phase connection in this embodiment includes a single-phase transformer A, a single-phase transformer B, and a same-phase power supply device. The same-phase power supply device includes a step-down transformer, an AC-DC-AC conversion device, and a matching transformer. The same-phase power supply device has an AC-DC-AC structure and is used to realize AC-DC-AC conversion.

[0036] See Figure 3 and Figure 4 The wiring configuration for the flexible single-phase connection structure is as follows:

[0037] The primary windings A and B of single-phase transformer A are connected to the incoming power grid phases A and B, respectively. The secondary windings a1x1 and a2x2 of single-phase transformer A are connected in parallel and are designated as parallel winding 1. The primary windings B and C of single-phase transformer B are connected to the incoming power grid phases B and C, respectively. The secondary windings b1y1 and b2y2 of single-phase transformer B are connected in parallel and are designated as parallel winding 2. Parallel winding 2 is connected in parallel with the same-phase power supply device and is designated as parallel same-phase winding, i.e., winding c1z1. Parallel winding 1 and parallel same-phase winding are connected in series, with the series connection point being the neutral point and grounded. The non-parallel connection point of parallel winding 1 is connected to bus T to supply power to the contact network, and the non-series connection point of parallel same-phase winding is connected to bus F to supply power to the positive feeder.

[0038] Specifically, the x1 and x2 terminals of the secondary side of single-phase transformer A are connected to the c1 terminal of the parallel in-phase winding and then connected to the grounding R; the a1 and a2 terminals of the secondary side of single-phase transformer A are connected to the contact network T; the z1 terminal of the parallel in-phase winding is connected to the positive feeder F; the y1 and y2 terminals of the secondary side of single-phase transformer B are connected to the in-phase power supply device; and the b1 and b2 terminals of the secondary side of single-phase transformer B are connected to the in-phase power supply device.

[0039] See Figure 3 and Figure 5 Schematic diagram of the phase angle of single-phase transformer A connection Figure 5 As shown in Figure a, the phase angle between phases AB and CB on the primary side of single-phase transformer A is 60 degrees. The a1(a2)x1(x2) winding after the parallel connection of the secondary side windings a1x1 and a2b2 of single-phase transformer A is in phase with phase AB.

[0040] Single-phase transformer B connection phase angle diagram Figure 5As shown in FIG. 1B, the phase angle between the primary side AB phase and CB phase of the single-phase transformer B is 60 degrees, the y2 (y1) b1 (b2) winding after the parallel connection of the secondary side b1y1 winding and b2y2 winding of the single-phase transformer B is consistent with the CB phase; the same-phase power supply device shifts the power supply phase input by the y2 (y1) b1 (b2) winding by 120 degrees to obtain the power supply z1c1, the c1z1 winding is connected in series with the a1 (a2) x1 (x2) winding, the series connection point x1 (x2) c1 is grounded, the phase difference between a1 (a2) and z1 terminal is 180 degrees, which corresponds to 27.5 kV and -27.5 kV respectively, and the same-phase power supply device is used for supplying power to the catenary T and the positive feeder F respectively.

[0041] In the embodiment of the present application, the working principle is as follows:

[0042] Transformer group reconstruction: disconnect all the secondary winding series connection points in the original Vx wiring, and change the series connection of the secondary winding of the two single-phase transformers A and B to parallel connection, that is, the x1 and x2 ends of the a1x1 and a2x2 windings of the single-phase transformer A are short-circuited, the a1 and a2 ends are connected in parallel to output, the a1x1 and a2x2 windings are connected in parallel to form parallel winding 1 (the phase is kept as AB phase) through phase conversion; the y1 and y2 ends of the b1y1 and b2y2 windings of the single-phase transformer B are short-circuited, the b1 and b2 ends are connected in parallel to output, the b1y1 and b2y2 windings are connected in parallel to form parallel winding 2 (the phase is kept as CB phase); the parallel connection point of the parallel winding 2 is connected to the input side of the same-phase power supply device, and the output voltage phase of the same-phase power supply device is adjusted by 180° through the AC / DC / AC conversion device to form a parallel same-phase winding which is complementary to the parallel winding 1.

[0043] Same-phase power supply device reconstruction: the same-phase power supply device is a step-down transformer, the input side of which is connected to the parallel winding 2, and the output side of which is connected to the AC / DC / AC conversion device, and the voltage level is reduced from 27.5 kV to a voltage level suitable for power electronic devices; the AC / DC / AC conversion device includes a rectifier, a DC bus and an inverter, and realizes 120° phase shift; the matching transformer is connected to the output of the inverter at the input side, and is stepped up to 27.5 kV and outputs the z1c1 winding. The AC / DC / AC conversion device is provided with a harmonic suppression module, and the total harmonic distortion rate of the output is less than 3%; and the AC / DC / AC conversion device adopts a three-level NPC topology structure, and realizes phase dynamic adjustment through SPWM modulation, and the adjustment range is ±5°.

[0044] System integration: the parallel winding 1 and the parallel winding 2 together form a 2×25 kV power supply architecture, and the dynamic current distribution between the two windings is realized by controlling the voltage amplitude and phase of the parallel same-phase winding. Specifically, the x1 / x2 terminal of the parallel winding 1 is connected in series with the c1 terminal of the parallel same-phase winding and then grounded; the output end a1 / a2 terminal of the transformer A is connected to the T bus (+27.5 kV) to supply power to the catenary; the output end z1 terminal of the same-phase power supply device is connected to the F bus (-27.5 kV) to supply power to the positive feeder, and finally a 2×27.5 kV power supply architecture with a phase difference of 180° is formed.

[0045] When the phase power supply device fails, the system directly switches to the standby mode: the phase power supply device and the single-phase transformer B connected in parallel with the phase power supply device are taken out of operation, the single-phase transformer A is still in operation, the two windings of the single-phase transformer A are adjusted from parallel connection to series connection, the series connection point is grounded, and the non-series connection points of the two windings are connected to the T bus and the F bus respectively.

[0046] It should be noted that in this document, the terms "comprise", "comprising", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, alternatives, and variations can be made in the embodiments without departing from the spirit and scope of the present application as defined by the appended claims and their equivalents.

Claims

1. A structure for converting a Vx wiring traction transformer into a flexible single-phase wiring, based on a single-phase transformer A, a single-phase transformer B and a same-phase power supply device, characterized in that, a1x1 winding and a2x2 winding on the secondary side of the transformer A are connected in parallel to form parallel winding 1; b1y1 winding and b2y2 winding on the secondary side of the transformer B are connected in parallel to form parallel winding 2; the parallel winding 2 and the same-phase power supply device are connected in parallel to form parallel same-phase winding; the parallel winding 1 and the parallel same-phase winding are connected in series, the series connection point is grounded, and the non-series connection points are respectively connected to the overhead line and the positive feeder to form a 2×27.5kV power supply structure; the same-phase power supply device comprises a step-down transformer, an AC-DC-AC conversion device and a matching transformer connected in sequence, which is used to offset the input voltage phase of the parallel winding 2 by 120°, and output a voltage with a phase difference of 180° from the parallel winding 1; the phase of the parallel winding 1 is consistent with the primary side AB phase of the same-phase transformer A, and the phase of the parallel same-phase winding is 180° different from the primary side CB phase of the same-phase transformer B after phase shifting by the same-phase power supply device.

2. The structure according to claim 1, characterized in that, a step-down transformer, the input side of which is connected to the parallel winding 2, and the output side of which is connected to the AC-DC-AC conversion device; an AC-DC-AC conversion device, which comprises a rectifier, a DC bus and an inverter, and is used to realize a 120° basic phase offset; a matching transformer, the input side of which is connected to the inverter output, and the output side of which generates z1c1 winding.

3. The structure of claim 2, wherein The AC-DC-AC conversion device adopts a three-level NPC topology structure, and realizes phase dynamic adjustment through SPWM modulation, with an adjustment range of ±5°.

4. The structure of claim 2, wherein The AC-DC-AC conversion device is configured with a harmonic suppression module, and the total harmonic distortion rate of the output is less than 3%.

5. The structure according to claim 1, characterized in that, the primary side of the transformer A and the primary side of the transformer B are respectively connected to the AB phase and the CB phase of a three-phase power grid; the secondary side forms a 2×27.5kV output through parallel-serial reconstruction and the same-phase power supply device, and the neutral point is grounded through a non-linear resistor.

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