Electrified railway through type same phase power supply system structure

Abstract

The application discloses a kind of electrified railway through type same phase power supply system structure, including same phase power supply device CPD, traction secondary bus, single-phase voltage source converter and single-phase transformer;Traction secondary bus is connected in traction port of traction transformer secondary side by circuit breaker;The DC side of single-phase voltage source converter is connected with the DC link of same phase power supply device CPD, and the AC side is connected with single-phase transformer, and the other side of single-phase transformer is connected between traction secondary bus and traction bus;The amplitude and phase of traction bus voltage are adjusted by adjusting the AC side voltage of single-phase voltage source converter;Traction bus voltage uses voltage phase-active power and voltage amplitude-reactive power droop control.Can realize the through type same phase power supply of traction network, reduce or eliminate crossing power, improve the regenerative energy utilization rate of traction power supply system, with less investment, higher reliability.

Description

Technical Field

[0001] This invention belongs to the field of traction power supply technology, and in particular relates to the structure of a through-type in-phase power supply system for electrified railways. Background Technology

[0002] The traction power supply system consists of traction substations and the traction network. To reduce the negative sequence impact of the traction power supply system on the power system, traction transformers generally use a rotating connection method to connect to the power system. The secondary side of a traction transformer typically has at least two ports, supplying power to the traction networks on either side. A sectioning station is located between two adjacent traction substations. Electrical phase separation occurs at the exit of the traction substation and at the sectioning station. When a train passes through an electrical phase separation, it is prone to problems such as electric arcing and burnt-out traction network suspension cables.

[0003] To eliminate the adverse effects of phase separation, two methods are generally used: one is to employ automatic phase separation technology, and the other is to use in-phase power supply technology. In-phase power supply technology can currently be mainly divided into two categories:

[0004] 1) One port on the secondary side of the traction transformer is the traction power supply port, used to supply power to the traction load; the other port is the compensation port. A back-to-back converter is installed between these two ports to realize the transfer of active power and the compensation of reactive power and harmonics, so as to reduce the impact of the traction power supply system on the power quality of the power system, such as negative sequence and harmonics.

[0005] 2) Use AC-DC-AC conversion technology. The electrical energy of the power system is transmitted to the traction substation via three-phase transmission lines. The traction substation consists of a three-phase traction transformer, a three-phase converter rectifier stage, and a single-phase converter inverter stage, which rectifies the electrical energy into DC and then inverts it into single-phase AC to supply power to the traction load.

[0006] Of the two in-phase power supply schemes mentioned above, scheme 1) is cheaper, while scheme 2 is more expensive; scheme 1) cannot automatically adjust the phase of the traction bus voltage. In actual engineering, traction transformers are generally connected to the nearest 110kV or 220kV bus of the power system. Two adjacent traction substations may be powered by 110kV or 220kV buses from different substations within the same power system. The high-voltage side voltages of two adjacent traction transformers generally have a phase difference. If bilateral power supply or even through-type in-phase power supply is implemented between two adjacent traction substations, due to the incomplete in-phase operation of the traction bus voltages, a relatively large power flow will occur from the leading traction bus to the lagging traction bus. When the traction network is unloaded or lightly loaded, one traction substation draws active power, while the other returns active power. Power companies generally use a metering method that excludes reverse power flow, resulting in the traction power supply department having to pay electricity charges due to the power flow. Furthermore, dual-side power supply and through-type phase power supply will result in a low-voltage electromagnetic loop in the power system, and the power crossing may cause malfunctions in the power system's relay protection devices. The power crossing will also increase the losses in the traction network.

[0007] Option 2 can completely eliminate phase separation in the traction network and its negative sequence impact on the power system. Low-voltage electromagnetic loops can be avoided through proper control. However, it requires very large-capacity IGBTs and other switching devices, resulting in very high costs. For electrified railways, the economical through-type in-phase power supply solution is more valuable. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a structure for a through-type in-phase power supply system for electrified railways.

[0009] The present invention discloses a through-type in-phase power supply system for electrified railways, comprising an in-phase power supply device (CPD), a traction auxiliary bus, a single-phase voltage source converter, and a single-phase transformer.

[0010] The traction auxiliary busbar is located on the secondary side of the traction transformer and is connected to the traction port on the secondary side of the traction transformer via a circuit breaker.

[0011] A phase-in-phase power supply device (CPD) is installed between the two ports on the secondary side of the traction transformer. The phase-in-phase power supply device (CPD) consists of a back-to-back converter and a corresponding matching transformer. The traction port and the back-to-back converter are connected to a traction matching transformer (TMT), and the converter connected to the TMT is denoted as VSC2. The compensation port and the back-to-back converter are connected to a high-voltage matching transformer (HMT), and the converter connected to the HMT is denoted as VSC1.

[0012] The DC side of the single-phase voltage source converter is connected to the DC link of the same-phase power supply device (CPD), and the AC side is connected to the single-phase transformer. The other side of the single-phase transformer is connected in series between the traction auxiliary bus and the traction bus.

[0013] The control strategy of converter VSC1 is to adjust the power flowing through converter VSC1 according to the degree of asymmetry of the three-phase current of the high-voltage transmission line; the control strategy of converter VSC2 is to maintain the voltage stability of the DC link; the control strategy of the single-phase voltage source converter is to control the amplitude and phase of the traction bus voltage according to the active and reactive power fed out by the traction substation.

[0014] In a CPD (Concurrent Phase Power Distribution) system, if the rated voltage of the compensation port is low, the high-voltage matching transformer (HMT) should be removed.

[0015] For AT power supply mode, two voltage source converters are required, namely converter VSC3 and converter VSC4. The DC side of converter VSC3 and converter VSC4 is connected to the DC link of the same phase power supply device CPD, and the AC side is connected to single-phase transformer AMT1 and single-phase transformer AMT2 respectively. The other side of single-phase transformer AMT1 and single-phase transformer AMT2 are connected in series to the T line and F line between the traction power supply port of the traction transformer and the traction auxiliary bus.

[0016] The voltage amplitudes fed out by converters VSC3 and VSC4 are the same, but the phases are opposite. By adjusting the voltage amplitudes and phases of converters VSC3 and VSC4, the voltage amplitudes and phases of traction buses T and F can be adjusted.

[0017] The beneficial technical effects of this invention are as follows:

[0018] This invention enables continuous, phase-in-phase power supply to the traction network, reduces or eliminates crossing power, improves the regenerative energy utilization rate of the traction power supply system, requires less investment, and has high reliability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the overall implementation of a through-type in-phase power supply under a direct supply method.

[0020] Figure 2 This is a schematic diagram of the voltage regulation of the traction busbar in a traction substation under direct power supply mode.

[0021] Figure 3 This is a schematic diagram of the droop control of the traction bus voltage amplitude minus active power.

[0022] Figure 4 This is a schematic diagram of the droop control of the traction bus voltage phase versus reactive power.

[0023] Figure 5This is a schematic diagram illustrating the overall implementation of continuous in-phase power supply under AT power supply mode.

[0024] Figure 6 This is a schematic diagram of traction bus voltage regulation under AT power supply mode. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] The overall scheme for implementing through-type in-phase power supply under direct power supply mode in this invention is as follows: Figure 1 As shown:

[0027] One port on the secondary side of the traction transformer is the traction power supply port, used to supply power to the traction load; the other port is the compensation port. A traction auxiliary bus is added to the secondary side of the traction transformer. The traction auxiliary bus is connected to the traction port on the secondary side of the traction transformer via a circuit breaker. A phase-in-phase power supply device (CPD) is installed between the two ports on the secondary side of the traction transformer. The phase-in-phase power supply device consists of back-to-back converters and corresponding matching transformers, realizing active power transfer and reactive power and harmonic compensation, so as to reduce the impact of the traction power supply system on the power quality of the power system, such as negative sequence and harmonics. The traction matching transformer (TMT) is located between the traction port and the back-to-back converters. The high-voltage matching transformer (HMT) is located between the compensation port and the back-to-back converters. If the rated voltage of the compensation port is low, the HMT can be omitted. The back-to-back converters and the corresponding matching transformers are collectively referred to as the phase-in-phase power supply device (CPD). Among the back-to-back converters, the converter connected to the HMT is denoted as VSC1, and the converter connected to the TMT is denoted as VSC2.

[0028] In the back-to-back DC link of the CPD (Conductor Power Distribution Device), a single-phase voltage source converter (VSC3) and a single-phase transformer (AMT) are added. The DC side of the VSC3 is connected to the DC link of the CPD, and its AC side is connected to one side of the AMT. The other side of the AMT is connected in series between the traction auxiliary bus and the traction bus. By adjusting the AC output voltage of the VSC3, the amplitude and phase of the traction bus voltage can be adjusted.

[0029] The principle of traction bus voltage load and phase control is as follows: Figure 2 As shown. Among them, This is the voltage of the traction auxiliary bus, and this voltage is not adjustable. The voltage of the single-phase transformer AMT. This is the voltage of the traction bus. Because... Therefore, only the voltage needs to be adjusted appropriately. Voltage can be achieved by adjusting the amplitude and phase. The amplitude and phase are adjusted.

[0030] The traction bus voltage is controlled by droop adjustment based on voltage phase versus active power and traction bus voltage amplitude versus reactive power. The adjustment principle is as follows: Figure 3 , 4 As shown. Regarding the control principle of voltage phase-active power (such as...) Figure 3 The following measures are taken: When the active power output of the traction substation is high, the voltage phase of the traction bus should be appropriately reduced; conversely, when the reactive power output of the traction substation is high, the voltage amplitude of the traction bus should be appropriately reduced; conversely, when the reactive power output of the traction substation is high, the voltage amplitude of the traction bus should be appropriately reduced. Through the droop control of voltage phase versus active power and traction bus voltage amplitude versus reactive power, ride-through power can be reduced or eliminated, improving the regenerative energy utilization rate of the traction power supply system, and eliminating the need for communication between traction substations.

[0031] The maximum output voltage on the side where the AMT is connected to the traction busbar is related to the phase difference on the high-voltage side of each traction transformer. This voltage is generally low, at most a few kV. Although the entire load current flows through this side, its capacity is still relatively small. The capacity on the other side of the AMT and the capacity of VSC3 are also relatively small, so the total investment is also lower.

[0032] When VSC1 fails, VSC3 can still operate normally. VSC2 and VSC3 can be combined into a back-to-back converter and continue to operate normally. Similarly, when VSC2 fails, VSC1 and VSC3 can be combined into a back-to-back converter and continue to operate normally. This configuration will only fail when VSC3 fails, the AMT fails, or both VSC1 and VSC3 fail simultaneously, thus exhibiting high reliability.

[0033] In addition, traction substations should use traction transformers with high capacity utilization of compensation devices, such as Scott-connected, YNvd-connected, or YN2d-connected transformers. These types of traction transformers feed mutually perpendicular α-phase and β-phase voltages, while the traction network voltage is the sum (or difference) of the α-phase and β-phase voltages. Of course, other similar connection transformers can also be used.

[0034] In the AT power supply mode, this invention uses a YN2d traction transformer as an example to illustrate the implementation of continuous in-phase power supply, such as... Figure 5 As shown. Figure 4 Structure and Figure 1 The basic structure is the same, except that two single-phase voltage source converters, namely VSC3 and VSC4, and two single-phase transformers, namely ATM1 and ATM2, are required here. ATM1 and ATM2 are connected in series in the contact line T and positive feeder F of the AT traction network, respectively.

[0035] Under AT power supply mode, the traction bus adjustment principle is as follows: Figure 6 As shown. Among them, and These are the voltages of the traction auxiliary busbars T and F, respectively, and these voltages are not adjustable. and These are the output voltages of single-phase transformers AMT1 and ATM2, respectively. and These are the voltages of traction buses T and F, respectively. Because... (x = T, F), therefore only the voltage needs to be adjusted appropriately. and Voltage can be achieved by adjusting the amplitude and phase. The amplitude and phase are adjusted. It should be noted that before adjustment, After adjustment, it should be ensured that This requires Right now and The amplitudes are equal, but the voltage amplitudes are opposite.

[0036] Similarly, because VSC3 and VSC34 output lower voltages, their capacity is smaller, resulting in lower investment costs.

[0037] When VSC1 fails, VSC3 can still operate normally. VSC2 and VSC3 can be combined into a back-to-back converter and continue to operate normally. Similarly, when VSC2 fails, VSC1 and VSC3 can be combined into a back-to-back converter and continue to operate normally. This configuration will only fail when VSC3 fails, the AMT fails, or both VSC1 and VSC3 fail simultaneously, thus exhibiting high reliability.

Claims

1. A structure for a through-type in-phase power supply system for electrified railways, characterized in that, The device comprises a CPD, a traction secondary bus, a single-phase voltage source converter and a single-phase transformer; The traction secondary bus is arranged at the secondary side of the traction transformer, and the traction secondary bus is connected to the traction port of the secondary side of the traction transformer through a circuit breaker; A CPD is arranged between two ports of the secondary side of the traction transformer, and the CPD is composed 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 the converter connected to the TMT is denoted as VSC2; a high-voltage matching transformer HMT is arranged between the compensation port and the back-to-back converter, and the converter connected to the HMT is denoted as VSC1; A single-phase voltage source converter VSC3 and a single-phase transformer AMT are arranged on the DC link of the back-to-back converter in the CPD; the DC side of the single-phase voltage source converter VSC3 is connected to the DC link of the CPD, and the AC side of the single-phase voltage source converter VSC3 is connected to 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 phase of the traction bus voltage are adjusted by adjusting the output voltage of the AC side of the single-phase voltage source converter VSC3; when the VSC1 fails, the VSC3 can still work normally, and the combination of the VSC2 and the VSC3 as a back-to-back converter can still work normally; similarly, when the VSC2 fails, the combination of the VSC1 and the VSC3 as a back-to-back converter can still work normally; The control strategy of the converter VSC1 is to adjust the power flowing through the converter VSC1 according to the asymmetry degree of the three-phase current of the high-voltage transmission line; the control strategy of the converter VSC2 is to maintain the stability of the voltage of the DC link; and the control strategy of the single-phase voltage source converter VSC3 is to perform droop control on the amplitude and phase of the traction bus voltage according to the active and reactive power fed by the traction substation.

2. The structure of the electrified railway through-type cophase power supply system according to claim 1, characterized in that, In the CPD, if the rated voltage of the compensation port is low, the high-voltage matching transformer HMT is cancelled.

3. The structure of the electrified railway through-type cophase power supply system according to claim 1, characterized in that, For the AT power supply mode, two single-phase voltage source converters, i.e., a single-phase voltage source converter VSC3 and a single-phase voltage source converter VSC4, are needed, the DC sides of the single-phase voltage source converters VSC3 and VSC4 are connected to the DC link of the CPD, and the AC sides of the single-phase voltage source converters VSC3 and VSC4 are connected to single-phase transformers AMT1 and AMT2 respectively, and the other sides of the single-phase transformers AMT1 and AMT2 are connected in series to the T line and the F line between the traction supply port of the traction transformer and the traction secondary bus; The voltage amplitudes of the single-phase voltage source converters VSC3 and VSC4 are the same, and the phases are opposite, and the voltage amplitudes and phases of the traction buses T and F are adjusted by adjusting the voltage amplitudes and phases of the single-phase voltage source converters VSC3 and VSC4.

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