CN115189354A

CN115189354A - Through type cophase power supply system structure of electrified railway

Info

Publication number: CN115189354A
Application number: CN202210936705.9A
Authority: CN
Inventors: 马庆安; 刘炜; 杨钧清
Original assignee: Southwest Jiaotong University
Current assignee: Southwest Jiaotong University
Priority date: 2022-08-05
Filing date: 2022-08-05
Publication date: 2022-10-14

Abstract

The invention discloses a through type in-phase power supply system structure of an electrified railway, which comprises an in-phase power supply device CPD, a traction auxiliary bus, a single-phase voltage source converter and a single-phase transformer, wherein the traction auxiliary bus is connected with the single-phase voltage source converter; the traction auxiliary bus is connected to a traction port on the secondary side of the traction transformer through a breaker; the direct current side of the single-phase voltage source converter is connected with the direct current link of the in-phase power supply device CPD, the alternating current side of the single-phase voltage source converter is connected with the single-phase transformer, and the other side of the single-phase transformer is connected between the traction auxiliary bus and the traction bus in series; the voltage amplitude and the phase of a traction bus are adjusted by adjusting the alternating-current side voltage of the single-phase voltage source converter; the voltage of the traction bus adopts droop control of voltage phase-active power and voltage amplitude-reactive power. Through type in-phase power supply of a traction network can be realized, the through power is reduced or eliminated, the utilization rate of regenerated energy of a traction power supply system is improved, the investment is low, and the reliability is high.

Description

Through type cophase power supply system structure of electrified railway

Technical Field

The invention belongs to the technical field of traction power supply, and particularly relates to a through type in-phase power supply system structure of an electrified railway.

Background

The traction power supply system consists of a traction substation and a traction network. In order to reduce the negative sequence influence of the traction power supply system on the power system, the traction transformer is generally connected to the power system in a rotation connection mode. The secondary side of the traction transformer generally has at least two ports, which respectively supply power to the traction networks on both sides. And a subarea station is arranged between two adjacent traction substations. Electric phase splitting exists at the outlet of the traction substation and the subareas. When the train passes through the electric phase separation, electric arcs are easy to generate, and the hanger of the traction net is easy to burn.

To eliminate the adverse effects of electric phase separation, two methods are generally used: one adopts an automatic passing neutral section technology, and the other adopts a cophase power supply technology. In-phase power supply technologies can be mainly classified into two types:

1) One port of the secondary side of the traction transformer is a traction power supply port and is used for supplying power to a traction load; the other port is a compensation port. And a back-to-back converter is arranged between the two ports, so that the active power transmission and the reactive power and harmonic compensation are realized, and the influence of a traction power supply system on the negative sequence, harmonic and other electric energy qualities of the electric power system is reduced.

2) An ac-dc conversion technique is used. The electric energy of the electric power system is transmitted to a traction substation through a three-phase transmission line, the traction substation consists of a three-phase traction transformer, a three-phase converter rectification link and a single-phase converter inversion link, and the electric energy is rectified into direct current and then inverted into single-phase alternating current to supply power to a traction load.

In the two same-phase power supply schemes, the scheme 1) is low in cost, and the scheme 2) is high in cost; scheme 1) the phase of the traction bus voltage cannot be automatically adjusted. In practical engineering, the traction transformer is typically connected nearby to a 110kV or 220kV bus of the power system. Two adjacent traction substations may be powered by 110kV or 220kV buses of different substations of the same power system. The voltages on the high-voltage sides of two adjacent traction transformers are generally out of phase. If bilateral power supply or through-type in-phase power supply is implemented between two adjacent traction substations, a larger through power flows from a traction bus with a leading phase to a traction bus with a lagging phase because the no-load voltage of the traction bus is not completely in phase, and when a traction network is in no-load or light-load, active power is taken by one traction substation and the other traction substation returns active power. The electric power department generally uses a measurement mode of reverse transmission and non-counting to active power, so that the traction power supply department needs to pay the electric power charge caused by the passing power. In addition, the bilateral power supply and the through type in-phase power supply can cause a low-voltage electromagnetic ring network to exist in the power system, and the passing through power can possibly cause the misoperation of a relay protection device of the power system. The through power also increases the losses of the traction network.

Scheme 2) can eliminate the electric phase separation in the traction network and the negative sequence influence on the electric power system completely, can avoid the low pressure electromagnetism looped netowrk through reasonable control, but its required switching element such as IGBT is very big in capacity, and the cost is very high. For electrified railways, the economic through-type in-phase power supply implementation scheme has more application value.

Disclosure of Invention

In view of the defects of the prior art, the invention provides a through-type in-phase power supply system structure of an electrified railway.

The invention discloses a through type in-phase power supply system structure of an electrified railway, which comprises an in-phase power supply device CPD, a traction auxiliary bus, a single-phase voltage source converter and a single-phase transformer.

The traction auxiliary bus is arranged on the secondary side of the traction transformer and is connected with a traction port on the secondary side of the traction transformer through a breaker.

A CPD is installed between two ports of the secondary side of the traction transformer, the CPD consists of a back-to-back converter and a corresponding matching transformer, a TMT is arranged between the traction port and the back-to-back converter, and a converter connected with the TMT is marked as VSC2; a high-voltage matching transformer HMT is arranged between the compensation port and the back-to-back converter, and the converter connected with the HMT is marked as VSC1.

The direct current side of the single-phase voltage source converter is connected with the direct current link of the in-phase power supply device CPD, the alternating current side of the single-phase voltage source converter is connected with the single-phase transformer, and the other side of the single-phase transformer is connected between the traction auxiliary bus and the traction bus in series.

The control strategy of the converter VSC1 is to regulate the power flowing through the converter VSC1 according to the asymmetry degree of three-phase current of the high-voltage transmission line; the control strategy of the converter VSC2 is to maintain the voltage stability of a direct-current link; the control strategy of the single-phase voltage source converter is to carry out droop control on the amplitude and the phase of the traction bus voltage according to the active power and the reactive power fed out by the traction substation.

In the same-phase power supply device CPD, if the rated voltage of the compensation port is lower, the high-voltage matching transformer HMT is cancelled.

To AT power supply mode, need set up two voltage source converter, converter VSC3 and converter VSC4 promptly, the direct current side of converter VSC3 and converter VSC4 links to each other with cophase power supply unit CPD's direct current link, the alternating current side links to each other with single phase transformer AMT1 and single phase transformer AMT2 respectively, single phase transformer AMT1 and single phase transformer AMT2 opposite side concatenate on traction transformer pull power supply port and pull T line and the F line between the secondary bus.

The voltage amplitude that converter VSC3 and converter VSC4 presented is the same, and the phase place is opposite, through voltage amplitude, the phase place of adjusting converter VSC3 and converter VSC4, realizes pulling the regulation of voltage amplitude, the phase place of generating line T and F.

The beneficial technical effects of the invention are as follows:

the invention can realize through in-phase power supply of the traction network, reduce or eliminate the through power, improve the utilization rate of the regenerated energy of the traction power supply system, and has less investment and higher reliability.

Drawings

Fig. 1 is a general implementation diagram of a through-type in-phase power supply in a direct supply mode.

Fig. 2 is a schematic diagram of the traction bus voltage regulation of the traction substation in the direct supply mode.

Fig. 3 is a schematic diagram of the droop control of the traction bus voltage amplitude-active power.

Fig. 4 is a schematic view of the droop control of the traction bus voltage phase-reactive power of the traction bus voltage.

Fig. 5 is a general implementation diagram of through-type in-phase power supply in the AT power supply mode.

Fig. 6 is a schematic diagram of the adjustment of the traction bus voltage in the AT power supply mode.

Detailed Description

The invention is described in further detail below with reference to the drawings and the detailed description.

The general scheme of the through-type in-phase power supply implementation of the invention under the direct power supply mode is shown in figure 1:

one port of the secondary side of the traction transformer is a traction power supply port and is used for supplying power to a traction load; the other port is a compensation port. And a traction auxiliary bus is added on the secondary side of the traction transformer. The traction auxiliary bus is connected to a traction port on the secondary side of the traction transformer through a breaker. And a same-phase power supply device CPD is arranged between two ports on the secondary side of the traction transformer. The in-phase power supply device is composed of back-to-back converters and corresponding matching transformers, and achieves active power transmission and reactive power and harmonic compensation so as to reduce the influence of a traction power supply system on the negative sequence, harmonic and other electric energy qualities of a power system. And a traction matching transformer TMT is arranged between the traction side port and the back-to-back converter. And a high-voltage matching transformer HMT is arranged between the compensation port and the back-to-back converter. If the compensation port is rated at a lower voltage, the HMT may be cancelled. The back-to-back converters and the corresponding matching transformers are collectively referred to as a common-phase power supply device CPD. In the back-to-back converter, the converter that links to each other with HMT is marked VSC1, and the converter that links to each other with TMT is marked VSC2.

And a single-phase voltage source converter VSC3 and a single-phase transformer AMT are added on a back-to-back direct current link in the in-phase power supply device CPD. The direct current side of the single-phase voltage source converter VSC3 is connected with the direct current link of the in-phase power supply device CPD, and the alternating current side of the same is connected with one side of the single-phase transformer AMT. The other side of the single-phase transformer AMT is connected in series between the traction secondary bus and the traction bus. The amplitude and the phase of the traction bus voltage can be adjusted by adjusting the output voltage of the alternating current side of the single-phase voltage source converter VSC 3.

The principle of traction bus voltage load and phase control is shown in fig. 2. Wherein, the first and the second end of the pipe are connected with each other,

to pull the secondary bus voltage, the voltage is not adjustable.

Is the voltage of the single-phase transformer AMT,

is the traction bus voltage. Due to the fact that

Therefore, only the voltage needs to be properly adjusted

The amplitude and the phase of the voltage can realize the voltage

Amplitude and phase of the signal.

The traction bus voltage adopts droop control of voltage phase-active power and traction bus voltage amplitude-reactive power, and the adjustment principle is shown in figures 3 and 4. The control principle for voltage phase-active power (as in fig. 3) is as follows: when the active power output by the traction substation is large, the voltage phase of a traction bus is properly reduced; and vice versa. When the output reactive power of the traction substation is large, the voltage amplitude of a traction bus is properly reduced; and vice versa. Through droop control of voltage phase, active power, voltage amplitude of traction bus and reactive power, ride-through power can be reduced or eliminated, the utilization rate of regenerated energy of a traction power supply system is improved, and communication is not needed between traction substations.

The maximum value of the output voltage at the side where the AMT is connected with the traction bus is related to the phase difference of the high-voltage side of each traction transformer. The voltage is generally low, of the order of a few kV at maximum. Although the side flows the full load current, its capacity is still small. The capacity of the other side of the AMT and the capacity of the VSC3 are also smaller, so the total investment is also smaller.

When VSC1 broke down, VSC3 still can normally work, and VSC2 and VSC3 can make up into back to back converter, still can normally work. Similarly, when VSC2 breaks down, VSC1 and VSC3 can make up into back to back converter, still can normally work. The structure can only fail when the VSC3 fails or the AMT fails or the VSC1 and the VSC3 fail simultaneously, so the structure has high reliability.

In addition, the traction substation uses a traction transformer with high capacity utilization rate of a compensation device, such as a Scott connection transformer, an YNV connection transformer or an YN2d connection transformer. The traction transformer feeds out alpha phase voltage and beta phase voltage which are mutually vertical, and the traction network voltage is the sum (or difference) of the alpha phase voltage and the beta phase voltage. Of course other similar wiring transformers may be used.

In the AT power supply mode, the structure of the present invention will be described with reference to an YN2d traction transformer as an example to realize through-type in-phase power supply, as shown in fig. 5. The structure of fig. 4 is substantially the same as that of fig. 1, except that here two single-phase voltage source converters, i.e. VSC3 and VSC4, and two single-phase transformers, i.e. ATM1, AMT2, are required. ATM1 and ATM2 are connected in series in contact line T and positive feeder F of AT traction network respectively.

In the AT power supply mode, the principle of traction bus adjustment is shown in fig. 6. Wherein the content of the first and second substances,

and

the voltages of the traction secondary bus T and F, respectively, are not adjustable.

And

the output voltages of the single-phase transformers AMT1 and ATM2 respectively,

and

the voltages of the traction buses T and F, respectively. Due to the fact that

(x = T, F), so only the voltage needs to be adjusted appropriately

And

the amplitude and the phase of the voltage can realize the voltage

Amplitude and phase of the signal. It should be noted that, prior to adjustment,

after adjustment should be guaranteed

This requires that

Namely that

And

the amplitudes are equal and the voltage amplitudes are opposite.

Similarly, because the output voltage of the VSC3 and the VSC34 is lower, the capacity is smaller, and the investment is less

When VSC1 broke down, VSC3 still can normally work, and VSC2 and VSC3 can make up into back to back converter, still can normally work. Similarly, when VSC2 breaks down, VSC1 and VSC3 can make up into back-to-back converter, still can normally work. The structure can only fail when the VSC3 fails or the AMT fails or the VSC1 and the VSC3 fail simultaneously, so the structure has high reliability.

Claims

1. A through type cophase power supply system structure of an electrified railway is characterized by comprising a cophase power supply device CPD, a traction auxiliary bus, a single-phase voltage source converter and a single-phase transformer;

the traction auxiliary bus is arranged on the secondary side of the traction transformer and is connected with a traction port on the secondary side of the traction transformer through a breaker;

a same-phase power supply device CPD is arranged between two ports of the secondary side of the traction transformer, the same-phase power supply device CPD consists of a back-to-back converter and a corresponding matching transformer, a traction matching transformer TMT is arranged between the traction port and the back-to-back converter, and a converter connected with the TMT is marked as VSC2; a high-voltage matching transformer HMT is arranged between the compensation port and the back-to-back converter, and the converter connected with the HMT is marked as VSC1;

the direct current side of the single-phase voltage source converter is connected with the direct current link of the in-phase power supply device CPD, the alternating current side of the single-phase voltage source converter is connected with the single-phase transformer, and the other side of the single-phase transformer is connected between the traction auxiliary bus and the traction bus in series;

the control strategy of the converter VSC1 is to regulate the power flowing through the converter VSC1 according to the asymmetry degree of three-phase current of the high-voltage transmission line; the control strategy of the converter VSC2 is to maintain the voltage stability of a direct-current link; the control strategy of the single-phase voltage source converter is to carry out droop control on the amplitude and the phase of the voltage of the traction bus according to the active power and the reactive power fed out by the traction substation.

2. The through in-phase power supply system structure of the electrified railway according to claim 1, wherein in the in-phase power supply device CPD, if the rated voltage of the compensation port is low, the high voltage matching transformer HMT is eliminated.

3. The through-type in-phase power supply system structure of the electrified railway according to claim 1, characterized in that for the AT power supply mode, two voltage source converters are required, namely a converter VSC3 and a converter VSC4, the direct current sides of the converter VSC3 and the converter VSC4 are connected with the direct current link of the in-phase power supply device CPD, the alternating current sides are respectively connected with a single-phase transformer AMT1 and a single-phase transformer AMT2, and the other sides of the single-phase transformer AMT1 and the single-phase transformer AMT2 are connected in series with a T line and an F line between a traction power supply port and a traction secondary bus of the traction transformer;

the voltage amplitude that converter VSC3 and converter VSC4 presented is the same, and the phase place is opposite, through adjusting converter VSC3 and converter VSC 4's voltage amplitude, phase place, realizes pulling the regulation of the voltage amplitude, the phase place of generating line T and F.