Smart traction substation and its power flow control method

Abstract

The present invention provides a smart traction substation and a power flow control method thereof, which relates to the technical field of electric railway power supply. The present invention includes a traction transformer TT, a power flow control device PCD, and a controller CC, the traction transformer TT has a primary side connected to a three-phase power grid, one end of a secondary side connected to a traction bus TSB, and the other end grounded, the traction bus TSB is connected to a traction network OCS using bilateral power supply via a feeder F, the controller CC controls the power flow control device PCD to perform negative phase compensation for the traction transformer TT based on the power amount information of the traction bus TSB and the feeder F, so that the negative phase meets the national standard requirements, and the controller CC also controls the power flow control device PCD to utilize the generated power flow returning from the traction network OCS to the traction substation by feeding or storing energy in a power distribution system, so that the generated power flow returning to the power grid meets the preset requirements.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Chinese Patent Application No. 202210261839.5, filed on March 17, 2022, the contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of traction power supply for AC electric railways, and in particular to a smart traction substation and its power flow control method. [Background technology]

[0003] Electrical phase splitting in electric railways is the weakest link in the entire traction power supply system. The neutral section of the electrical phase split forms a dead section, causing power supply interruptions. While the dead section of the neutral section is typically only a few tens of meters, the power outage distance when trains are controlled to automatically pass through a phase split can reach 500 meters or more, significantly restricting the smooth operation of trains and even causing trains to stop on slopes when going uphill. In-phase power supply for electric railways eliminates electrical phase splitting at traction substations, while bilateral power supply eliminates electrical phase splitting at sections. The use of in-phase and bilateral power supply eliminates dead sections throughout the system, ensuring continuous power supply for trains while eliminating the risk of excessive phase splitting. In addition, by effectively extending the power supply arm, it reduces peak load, increases bottom load, smooths out fluctuations in traction load, increases the direct utilization rate of regenerative braking energy, saves power supply resources, reduces basic electricity charges, and helps solve problems with the quality of electric energy such as reverse phase. It also has the advantages of high power supply reliability, good power grid voltage level, high power supply capacity, and small power loss.

[0004] Typically, a bilateral power feed traction network forms a parallel structure with the power grid through traction substations on both sides. When the traction network is unloaded, power and current flow through it. This corresponding power flow is called the ride-through power flow (the corresponding current is called the balanced current). At this time, the ride-through power flows in from one traction substation and out from the other. That is, when the ride-through power flows from the power grid to the traction substation of the traction network, it is in a load (power consumption) state. When the ride-through power flows from the traction network to the traction substation of the power grid, it is in a power generation state. Because bilateral power feed changes the structure of the power grid, two key technical challenges must be overcome to implement bilateral power feed.

[0005] The first issue concerns the issue of relay protection for the power grid and traction network. Relay protection must have a broader protection scope and be able to trip the traction network in conjunction with the power grid to cut off the power flow when a fault occurs in the power grid. This can be perfectly resolved by arranging transmission line protection in the power grid and tiered protection in the traction network.

[0006] The second issue concerns the impact of ride-through power flow on the power grid and its metering. When ride-through power flow returns to the power grid, it is equivalent to power generation by the traction substation. If the backflow is metered backwards—that is, treated as power generation and offset against the power consumption of another traction substation—the user incurs no economic loss. If ride-through power flow is not metered or is metered forwards when returning to the power grid, it will result in economic losses for the user. In such cases, research is needed to find ways to reduce ride-through power flow in bilateral power supply or to utilize ride-through power flow to fully utilize the advantages of bilateral power supply while reducing the impact on the power grid and users and increasing the efficiency of power consumption.

[0007] Prior art has proposed several methods to suppress ride-through power flow. One, as in the Chinese patent "Bilateral Power Supply System for Electric Railways" (license publication number: CN103552488B), involves connecting a reactor in series with the secondary side of the traction transformer in the traction substation to reduce the balancing current. However, the drawbacks of this method are that the required reactor is relatively large and the train's power factor must be adjusted to a leading power factor; otherwise, this may affect the supply voltage and power capacity. Theoretically, ride-through power flow and balancing current cannot be reduced to zero unless the impedance on the secondary side of the traction transformer becomes infinite.

[0008] Aside from the current research into suppression technologies for ride-through power flow in bilateral power supply, we have proposed a smart traction substation and its power flow control method, which realizes in-phase bilateral feedthrough power supply for electric railways, eliminates electrical phase splitting, and eliminates dead sections. Furthermore, by utilizing the ride-through power flow of bilateral power supply returning to the power grid and the regenerative energy generated by braking electric locomotives in the traction network as the power flow, the power flow returning to the power grid can be made to meet preset requirements, such as zero, while compensating for excess negative phase and ensuring that the negative phase meets national standard requirements. Summary of the Invention [Problem to be solved by the invention]

[0009] The objectives of the present invention are to provide a smart traction substation and a power flow control method therefor that (1) enable the power flow in a traction substation to be controlled, (2) utilize the generated power flow from the traction network OCS returning to the power grid using bilateral power supply and the generated power flow caused by braking of electric locomotives in the traction network to ensure that the generated power flow returning to the power grid meets preset requirements, and (3) compensate for excess negative phase and ensure that the negative phase meets national standard requirements. [Means for solving the problem]

[0010] The present invention is achieved by the following technical solutions:

[0011] A smart traction substation including a traction transformer TT, The smart traction substation is provided with a power flow control device PCD and a controller CC. The primary side of the traction transformer TT is connected to the U and V phases of a three-phase power grid, one end of the secondary side is connected to a traction bus TSB, and the other end is grounded. The traction bus TSB is connected to an AC bilateral power supply traction network OCS via a feeder F. The controller CC controls the power flow control device PCD to perform negative phase compensation for the traction transformer TT based on the energy information of the traction bus TSB and the feeder F, so that the negative phase meets the national standard requirements. The controller CC also controls the power flow control device PCD to utilize the generated power flow from the AC bilateral power supply traction network OCS returning to the traction substation, so that the generated power flow returning to the power grid meets the preset requirements.

[0012] The feeder F includes a feeder F1 and a feeder F2, the traction network OCS includes a traction network OCS1 and a traction network OCS2, a traction bus TSB feeds the traction network OCS1 via the feeder F1, and the traction bus TSB feeds the traction network OCS2 via the feeder F2, and an electrical section is provided between the traction network OCS1 and the traction network OCS2.

[0013] A current transformer CT1 is provided on the feeder F1, a current transformer CT2 is provided on the feeder F2, and a voltage transformer PT is provided on the traction bus TSB, and measurement terminals of the current transformer CT1, the current transformer CT2, and the voltage transformer PT are all connected to input terminals of a controller CC, and a control terminal of the controller CC is connected to a control terminal of a power flow control device PCD.

[0014] The power flow control device PCD includes a converter device TPC, a converter device PPC, a converter device DPC, an energy storage device ES, a positive bus PB, and a negative bus NB, The converter device TPC is a single-phase converter system, one end of the AC side of which is connected to a traction bus TSB and the other end of which is grounded, The converter device PPC is a single-phase converter system, and one end of the AC side is directly connected to the W phase of the three-phase power grid and the other end is connected to the neutral wire N of the three-phase power grid, or the other end of the AC side of the converter device PPC is connected to the center tap O of the primary winding of the traction transformer TT; The converter device DPC is a three-phase converter system, and its AC side is connected to three-phase buses a, b, and c of a traction substation distribution system, respectively; The positive and negative poles of the DC sides of the converter devices PPC, TPC, DPC and energy storage device ES are connected to the positive bus PB and negative bus NB, respectively.

[0015] The control terminals of the power flow control device PCD include control terminals of a converter device TPC, a converter device PPC, a converter device DPC, and an energy storage device ES.

[0016] The present invention also provides The voltage transformer PT detects the voltage UT of the traction bus TSB, and the current transformers CT1 and CT2 detect the currents of the feeders F1 and F2, respectively; a step in which the controller CC calculates active power flows supplied from the traction bus TSB to the traction networks OCS1 and OCS2 via the feeders F1 and F2, respectively, based on the detected voltage of the traction bus TSB and the currents of the feeders F1 and F2, where the active power flows flowing through the traction networks OCS1 and OCS2 are positive and the active power flow flowing through the traction bus TSB is negative; The controller CC controls the converter device TPC and the converter device PPC of the power flow control device PCD based on the active power flow to perform negative phase compensation for the traction transformer TT so that the negative phase meets the national standard requirements, or the controller CC controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow from the traction network OCS1 and the traction network OCS2 returning to the traction substation so that the generated power flow returning to the power grid meets the preset requirements.

[0017] the controller CC calculates an active power flow P1 to be supplied from the traction bus TSB to the traction network OCS1 via the feeder F1 based on the voltage UT of the traction bus TSB and the current I1 of the feeder F1, and calculates an active power flow P2 to be supplied from the traction bus TSB to the traction network OCS2 via the feeder F2 based on the voltage UT of the traction bus TSB and the current I2 of the feeder F2; The controller CC controls the converter device TPC and the converter device PPC of the power flow control device PCD based on the active power flow P1 and the active power flow P2 to perform negative phase compensation for the traction transformer TT so that the negative phase meets the national standard requirements, or controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow returning from the traction network OCS1 and the traction network OCS2 to the traction substation so that the generated power flow returning to the power grid meets the preset requirements.

[0018] If P1+P2<0, the controller CC determines that the feeders F1 and F2 have returned the generated power flow to the power grid, and in this case, controls and operates the converter devices TPC and DPC of the power flow control device PCD to supply power to the three-phase buses a, b, and c of the power distribution system, or controls and charges the energy storage device ES of the converter device TPC, so that the sum of the generated power flows is equal to |P1+P2|, and the generated power flow returning to the power grid is 0, satisfying the preset requirement, and also controls and puts the converter device PPC of the power flow control device PCD into standby mode; If P1+P2>0, the controller CC determines that the feeders F1 and F2 meet the traction operation conditions, and in this case, controls the converter device PPC and the converter device TPC of the power flow control device PCD to perform negative phase compensation for the traction transformer TT, and controls the energy storage device ES of the power flow control device PCD to allow the converter device TPC to supply power to the traction bus TSB, so that the negative phase of the traction substation meets the standard, and controls the converter device DPC of the power flow control device PCD to be on standby; If P1+P2=0, the controller CC determines that the feeder F1 and the feeder F2 are unloaded, and in this case, controls the power flow control device PCD to wait. [Effects of the Invention]

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A smart traction substation is a substation capable of controlling power flow. By installing converter devices and energy storage devices, a new structure is formed, and after judgment and control, the ride-through power flow of bilateral power supply returning to the power grid and the regenerative power generated by braking electric locomotives in the traction network can all be used as power generation flow. The power generation flow returning to the power grid can be made zero or meet the requirements, and excessive negative phase can be compensated for, ensuring that the negative phase meets national standard requirements. 2. Without changing the power supply structure of the power grid to railways, the generated power flow of the traction network is utilized, eliminating the negative impact of ride-through power flow on the power grid and users, and fully realizing the benefits of bilateral power supply. 3. Implementing bilateral power supply between adjacent substations based on the in-phase power supply of the traction substation is more advantageous in utilizing the regenerative energy of the power supply arm, increasing the direct utilization rate of regenerative braking energy, and in normal cases, reducing the regenerative power and electrical energy returned to the power grid to zero. 4. The power flow control device can be connected to the traction substation energy storage device and distribution system to supply power, and in addition to utilizing ride-through power flow, it can also utilize surplus regenerative braking electrical energy. 5. By multiplexing the in-phase power supply and generation power flow utilization equipment of the traction substation, equipment duplication and investment can be reduced. 6. The technology is advanced, reliable and easy to implement. [Brief explanation of the drawings]

[0020] The accompanying drawings are used to provide a further understanding of embodiments of the present invention, constitute a part of the specification, and together with the following detailed description are used to explain, but not to limit, embodiments of the present invention.

[0021] [Figure 1]1 is a structural schematic diagram of an example of the present invention. [Figure 2] FIG. 2 is another structural schematic diagram of the present invention. [Figure 3] 2 is a schematic diagram showing the connection of control terminals of the power flow control device PCD of the present invention. FIG. [Figure 4] 3 is a flowchart of a control method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to make the technical aspects of the present invention more readily understandable to those skilled in the art, the present invention will be further described below with reference to the drawings and specific embodiments.

[0023] Example 1 As shown in FIG. 1, this embodiment provides a smart traction substation including a traction transformer TT, the smart traction substation being provided with a power flow control device PCD and a controller CC. The primary side of the traction transformer TT is connected to the U and V phases of a three-phase power grid, one end of the secondary side is connected to a traction bus TSB, and the other end is grounded. The traction bus TSB is connected to an AC bilateral power supply traction network OCS via a feeder F. The controller CC controls the power flow control device PCD to perform negative phase compensation for the traction transformer TT based on the energy information of the traction bus TSB and the feeder F, so that the negative phase meets the national standard requirements. The controller CC also controls the power flow control device PCD to utilize the generated power flow from the AC bilateral power supply traction network OCS returning to the traction substation, so that the generated power flow returning to the power grid meets the preset requirements.

[0024] In this embodiment, the power flow control device PCD is used to perform phase-sequence compensation for the traction transformer TT, and the phase-sequence meets the national standard requirements. This allows the smart traction substation of this embodiment to achieve in-phase power supply and eliminate electrical phase splitting at the substation. Bilateral power supply is used in the traction network OCS, eliminating electrical phase splitting in the section between the two substations, thereby enabling direct power supply of the entire traction network.

[0025] A traction power supply system implementing bilateral power supply includes two or more traction substations. In a specific smart traction substation shown in Figure 1, if the power flow from the smart traction substation back to the power grid is considered as the generated power flow, a ride-through power flow occurs in the traction network OCS due to the use of bilateral power supply. In this case, the power flow control device PCD uses the ride-through power flow flowing from this smart traction substation to the power grid as the generated power flow. In reality, the regenerative power flow generated when the locomotive brakes also flows from the smart substation to the power grid, or as the regenerative power flow. If the power flow is not completely absorbed by the accompanying traction locomotive and excess regenerative power also flows into the power grid, the regenerative power flow or excess regenerative power flow from the smart substation to the power grid is superimposed on the ride-through power flow and treated as the total generated power flow by the controller CC. The controller CC controls the power flow control device PCD to utilize the total generated power flow so that the generated power flow returning to the power grid meets a preset requirement, where the preset requirement may be to control the generated power flow returning to the power grid within a specific range or to make the generated power flow returning to the power grid zero. In the specific smart traction substation shown in Figure 1, when the power flow of the smart traction substation is put into traction state, a ride-through power flow occurs in the traction network OCS due to the use of bilateral power supply. In this case, the power flow control device PCD performs negative sequence compensation on the traction transformer TT of the smart traction substation so that the negative sequence meets the national standard requirement. In the particular smart traction substation shown in FIG. 1, when the power flow of the smart traction substation is set to 0, the power flow control device PCD goes into standby.

[0026] This embodiment utilizes the generated power flow returning to the smart traction substation without changing the power supply structure of the power grid to the railway, effectively eliminating the negative impacts on the power grid and users of the ride-through power flow and regenerative power flow caused by bilateral power supply, and fully demonstrating the benefits of bilateral power supply.In addition, this embodiment uses a power flow control device PCD to perform negative-phase compensation and generated power flow utilization, thereby multiplexing the in-phase power supply and generated power flow utilization device of the smart traction substation, effectively reducing equipment duplication and investment.

[0027] Furthermore, although the Background Art describes the need to reduce the balancing current by connecting a reactor in series to the secondary side of the traction transformer of the traction substation, this measure is not essential in this embodiment, i.e., this measure may or may not be adopted in this embodiment. The core of this embodiment is to utilize the generated power flow returning to the substation. With the use of bilateral power supply, ride-through power flow is inevitably present. In this embodiment, the focus is not on suppressing the occurrence of ride-through power flow but on dealing with the result of ride-through power flow, which is one of the keys that distinguish this embodiment from the prior art.

[0028] Preferably, in this embodiment, the feeder F includes a feeder F1 and a feeder F2, the traction network OCS includes a traction network OCS1 and a traction network OCS2, the traction bus TSB feeds the traction network OCS1 via the feeder F1, and the traction bus TSB feeds the traction network OCS2 via the feeder F2, and an electrical section is provided between the traction network OCS1 and the traction network OCS2.

[0029] In this embodiment, the smart substation uses in-phase power supply technology and the traction network OCS uses bilateral power supply technology to extend the power supply arm, allowing the traction train among the accompanying trains to more efficiently absorb the regenerative power flow of the braking train, increasing the direct utilization rate of regenerative braking energy and ultimately significantly reducing, or even eliminating, the regenerative power flow returning to the power grid. To facilitate maintenance, this embodiment may also install an electrical section in the traction network OCS of the substation, i.e., between traction network OCS1 and traction network OCS2. The installation of the electrical section, combined with sectioning measurement, control, and protection technology, prevents train power outages and facilitates inspection and maintenance.

[0030] Preferably, the feeder F1 is provided with a current transformer CT1, the feeder F2 is provided with a current transformer CT2, and the traction bus TSB is provided with a voltage transformer PT, and measurement terminals of the current transformer CT1, the current transformer CT2, and the voltage transformer PT are all connected to input terminals of the controller CC, and the control terminals of the controller CC are connected to control terminals of the power flow control device PCD.

[0031] Preferably, the power flow control device PCD in this embodiment includes a converter device TPC, a converter device PPC, a converter device DPC, an energy storage device ES, a positive bus PB and a negative bus NB; The converter unit TPC is a single-phase converter system, one end of the AC side of which is connected to the traction bus TSB and the other end is grounded. The converter device PPC is a single-phase converter system, and one end of the AC side is directly connected to the W phase of the three-phase power grid and the other end is connected to the neutral wire N of the three-phase power grid, or the other end of the AC side of the converter device PPC is connected to the center tap O of the primary winding of the traction transformer TT; The converter device DPC is a three-phase converter system, and its AC side is connected to the three-phase bus a, bus b, and bus c of the traction substation distribution system, respectively. The positive and negative poles of the DC sides of the converter devices PPC, TPC, DPC and energy storage device ES are connected to the positive bus PB and negative bus NB, respectively.

[0032] Here, as shown in FIG. 1, the three-phase power grid includes U phase, V phase, and W phase, and the primary side of the traction transformer TT may be connected to the U phase and the V phase of the three-phase power grid, one end of the AC side of the converter device PPC may be connected to the W phase of the three-phase power grid, and the other end of the AC side of the converter device PPC may be connected to the neutral line (i.e., the N line in FIG. 1), or may be connected to the center tap O of the primary winding of the traction transformer TT as shown in FIG. 2.

[0033] Preferably, the control terminals of the power flow control device PCD include control terminals of the converter device TPC, the converter device PPC, the converter device DPC and the energy storage device ES.

[0034] Here, as shown in FIG. 3, the control terminals of the converter device TPC, the converter device PPC, the converter device DPC, and the energy storage device ES of the power flow control device PCD are all connected to the control terminals of the controller CC, that is, the control terminals of the controller CC are connected to the control terminals of the power flow control device PCD.

[0035] From the above, the smart traction substation according to the embodiment of the present invention has the following advantages. 1. The smart traction substation of an embodiment of the present invention is a substation capable of controlling power flow, in which a converter device and an energy storage device are installed to form a new structure, which can utilize, after judgment and control, the ride-through power flow of bilateral power supply returning to the power grid and the regenerative power generated by braking the electric locomotive in the traction network as the power generation flow, so that the power generation flow returning to the power grid can be zero or meet the requirements, and excessive negative phase can be compensated for so that the negative phase meets national standard requirements. 2. Without changing the power supply structure of the power grid to railways, the generated power flow of the traction network is utilized, eliminating the negative impact of ride-through power flow on the power grid and users, and fully realizing the benefits of bilateral power supply. 3. Implementing bilateral power supply between adjacent substations based on the in-phase power supply of the traction substation is more advantageous in utilizing the regenerative energy of the power supply arm, increasing the direct utilization rate of regenerative braking energy, and in normal cases, reducing the regenerative power and electrical energy returned to the power grid to zero. 4. The power flow control device can be connected to the traction substation energy storage device and distribution system to supply power, and in addition to utilizing ride-through power flow, it can also utilize surplus regenerative braking electrical energy. 5. By multiplexing the in-phase power supply and generation power flow utilization equipment of the traction substation, equipment duplication and investment can be reduced. 6. The technology is advanced, reliable and easy to implement.

[0036] Example 2 As shown in FIG. 4 , this embodiment provides a control method based on the smart traction substation according to embodiment 1, including the following steps:

[0037] Step S100: The voltage transformer PT detects the voltage UT of the traction bus TSB, and the current transformers CT1 and CT2 detect the currents of the feeders F1 and F2, respectively.

[0038] Step S200: The controller CC calculates the active power flow that the traction bus TSB supplies to the traction networks OCS1 and OCS2 via the feeders F1 and F2 from the detected voltage of the traction bus TSB and the currents of the feeders F1 and F2, respectively. The active power flow flowing to the traction networks OCS1 and OCS2 is positive, and the active power flow flowing to the traction bus TSB is negative.

[0039] Step S300: Based on the active power flow, the controller CC controls the converter device TPC and the converter device PPC of the power flow control device PCD to perform negative phase compensation for the traction transformer TT, so that the negative phase meets the national standard requirements; or the controller CC controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow from the traction network OCS1 and the traction network OCS2 back to the traction substation, so that the generated power flow back to the power grid meets the preset requirements.

[0040] Preferably, the control method includes: The controller CC calculates an active power flow P1 that the traction bus TSB supplies to the traction network OCS1 via the feeder F1 from the voltage UT of the traction bus TSB and the current I1 of the feeder F1, and calculates an active power flow P2 that the traction bus TSB supplies to the traction network OCS2 via the feeder F2 from the voltage UT of the traction bus TSB and the current I2 of the feeder F2; The controller CC controls the converter device TPC and the converter device PPC of the power flow control device PCD based on the active power flow P1 and the active power flow P2 to perform negative phase compensation for the traction transformer TT so that the negative phase meets the national standard requirements, or controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow returning from the traction network OCS1 and the traction network OCS2 to the traction substation so that the generated power flow returning to the power grid meets the preset requirements.

[0041] Preferably, the method comprises: If P1+P2<0, the controller CC determines that the feeders F1 and F2 have returned the generated power flow to the power grid, and in this case, controls and operates the converter devices TPC and DPC of the power flow control device PCD to supply power to the three-phase buses a, b, and c of the power distribution system, or controls and charges the energy storage device ES of the converter device TPC, so that the sum of the generated power flows is equal to |P1+P2|, and the generated power flow returning to the power grid is 0, satisfying the preset requirement, and also controls and puts the converter device PPC of the power flow control device PCD into standby mode; If P1+P2>0, the controller CC determines that the feeders F1 and F2 meet the traction operation conditions, and in this case, controls the converter device PPC and the converter device TPC of the power flow control device PCD to perform negative phase compensation for the traction transformer TT, and controls the energy storage device ES of the power flow control device PCD to allow the converter device TPC to supply power to the traction bus TSB, so that the negative phase of the traction substation meets the standard, and controls the converter device DPC of the power flow control device PCD to be on standby; If P1+P2=0, the controller CC determines that the feeder F1 and the feeder F2 are unloaded, and in this case, controls the power flow control device PCD to wait.

[0042] The above is merely a preferred embodiment of the present invention, and the above preferred embodiment should not be considered as a limitation on the present invention, and the protection scope of the present invention is in accordance with the scope defined in the claims. Those skilled in the art may make some improvements and modifications without departing from the spirit and scope of the present invention, and these improvements and modifications shall also be considered as the protection scope of the present invention.

Claims

1. A smart traction substation including a traction transformer TT, The smart traction substation is provided with a power flow control device PCD and a controller CC, the primary side of the traction transformer TT is connected to the U-phase and V-phase of a three-phase power grid, one end of the secondary side is connected to a traction bus TSB and the other end is grounded, the traction bus TSB is connected to a traction network OCS using AC bilateral power supply via a feeder F, the controller CC controls the power flow control device PCD to perform negative phase compensation for the traction transformer TT based on power amount information of the traction bus TSB and the feeder F so that the negative phase meets national standard requirements, and the controller CC also controls the power flow control device PCD to utilize the generated power flow returning from the AC bilateral power supply traction network OCS to the traction substation by supplying power to or storing energy in a power distribution system, so that the generated power flow returning to the power grid meets predetermined requirements.

2. The power flow control device PCD includes a converter device TPC, a converter device PPC, a converter device DPC, a positive bus PB, and a negative bus NB, The converter device TPC is a single-phase converter system, one end of which is connected to a traction bus TSB and the other end of which is grounded. the converter device PPC is a single-phase converter system, and one end of the AC side is directly connected to a W phase of a three-phase power grid and the other end is connected to a neutral wire N of the three-phase power grid, or the other end of the AC side of the converter device PPC is connected to a center tap O of a primary winding of a traction transformer TT; The converter device DPC is a three-phase converter system, and its AC side is connected to three-phase buses a, b, and c of a traction substation power distribution system, respectively; The smart traction substation according to claim 1, wherein the positive and negative poles of the DC sides of the converter devices PPC, TPC, and DPC are connected to the positive bus PB and negative bus NB, respectively.

3. The smart traction substation according to claim 2, further comprising an energy storage device ES, the positive and negative poles of which are connected to the positive bus PB and the negative bus NB, respectively, on the DC side.

4. The smart traction substation according to claim 3, wherein the control terminals of the power flow control device PCD include control terminals of a converter device TPC, a converter device PPC, a converter device DPC, and an energy storage device ES.

5. The smart traction substation according to claim 3 or 4, characterized in that the feeders F include feeders F1 and F2, the traction network OCS includes traction networks OCS1 and OCS2, a traction bus TSB feeds traction network OCS1 via feeder F1, and the traction bus TSB feeds traction network OCS2 via feeder F2, and an electrical section is provided between traction network OCS1 and traction network OCS2.

6. The smart traction substation according to claim 5, wherein the feeder F1 is provided with a current transformer CT1, the feeder F2 is provided with a current transformer CT2, and the traction bus TSB is provided with a voltage transformer PT, measurement terminals of the current transformer CT1, the current transformer CT2, and the voltage transformer PT are all connected to input terminals of a controller CC, and a control terminal of the controller CC is connected to a control terminal of a power flow control device PCD.

7. 7. A power flow control method based on smart traction substation according to claim 6, comprising: The voltage transformer PT detects the voltage UT of the traction bus TSB, and the current transformers CT1 and CT2 detect the currents of the feeders F1 and F2, respectively; a step in which the controller CC calculates active power flows supplied from the traction bus TSB to the traction networks OCS1 and OCS2 via the feeders F1 and F2, respectively, based on the detected voltage of the traction bus TSB and the currents of the feeders F1 and F2, wherein the active power flows flowing through the traction networks OCS1 and OCS2 are positive and the active power flow flowing through the traction bus TSB is negative; the controller CC controls the converter devices TPC and PPC of the power flow control device PCD based on the active power flow to perform negative phase compensation for the traction transformer TT, so that the negative phase meets the national standard requirements; or the controller CC controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow returning from the traction network OCS1 and the traction network OCS2 to the traction substation, so that the generated power flow returning to the power grid meets the preset requirements.

8. The controller CC calculates an active power flow P1 that the traction bus TSB supplies to the traction network OCS1 via the feeder F1 from the voltage UT of the traction bus TSB and the current I1 of the feeder F1, and calculates an active power flow P2 that the traction bus TSB supplies to the traction network OCS2 via the feeder F2 from the voltage UT of the traction bus TSB and the current I2 of the feeder F2; 8. The power flow control method according to claim 7, wherein the controller CC controls the converter devices TPC and PPC of the power flow control device PCD according to the active power flow P1 and the active power flow P2 to perform negative phase compensation for the traction transformer TT, so that the negative phase meets the national standard requirements, or controls the converter device DPC or the energy storage device ES of the power flow control device PCD to utilize the total generated power flow from the traction network OCS1, the traction network OCS2 returning to the traction substation, so that the generated power flow returning to the power grid meets the preset requirements.

9. If P1+P2<0, the controller CC determines that the feeders F1 and F2 have returned the generated power flow to the power grid, and in this case, controls and operates the converter devices TPC and DPC of the power flow control device PCD to supply power to the three-phase buses a, b, and c of the power distribution system, or controls and charges the energy storage device ES of the converter device TPC, so that the sum of both generated power flows is equal to |P1+P2|, and the generated power flow returning to the power grid is 0, satisfying the preset requirement, and also controls the converter device PPC of the power flow control device PCD to be on standby; If P1+P2>0, the controller CC determines that the feeders F1 and F2 meet the traction operation conditions, and in this case, controls the converter devices PPC and TPC of the power flow control device PCD to perform negative phase compensation on the traction transformer TT, and controls the energy storage device ES to allow the converter device TPC to supply power to the traction bus TSB, so that the negative phase of the traction substation meets the standard, and controls the converter device DPC of the power flow control device PCD to be on standby; 9. The power flow control method according to claim 8, wherein when P1+P2=0, the controller CC determines that the feeder F1 and the feeder F2 are unloaded, and in this case, controls the power flow control device PCD to put them into standby.

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