Smart traction substation and power flow control method thereof

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 of electric railway is the weakest part of the entire traction power supply system. The neutral section of electrical phase splitting forms a dead section, which causes power supply interruption. The dead section of the neutral section is generally only a few tens of meters, but the blackout distance of controlling the train to pass through the automatic phase splitting can reach more than 500 meters, which severely restricts the good operation of the train and even causes the train to stop on the slope when going uphill. The in-phase power supply of electric railway can eliminate the electrical phase splitting where the traction substation is located, and the bilateral power supply can eliminate the electrical phase splitting where the section is located. The adoption of in-phase power supply and bilateral power supply can eliminate the dead section throughout, ensure the continuous power supply of the train, and at the same time eliminate the risk of excessive phase splitting. In addition, by effectively extending the power supply arm, it can reduce the peak load, increase the bottom load, smooth out the fluctuation of the traction load, increase the direct utilization rate of the regenerative braking energy, save power supply resources, reduce the basic electricity fee, and help solve problems of the quality of electric energy such as reverse phase. It has the advantages of high power supply reliability, good voltage level of the power grid, high power supply capacity, and small power loss.

[0004] Usually, bilateral power supply traction network forms a parallel structure with the power grid through traction substations on both sides. When the traction network is unloaded, there is a power flow and a current in the traction network, and 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 flow flows in from the traction substation on one side and flows out from the traction substation on the other side, that is, when the ride-through power flow flows from the power grid to the traction substation of the traction network, it is in a load (power consumption) state, and when the ride-through power flow flows from the traction network to the traction substation of the power grid, it is in a power generation state. Because bilateral power supply has changed the structure of the power grid, two important technical problems need to be solved to implement bilateral power supply.

[0005] The first issue is the problem of relay protection of the power grid and the traction network. The relay protection needs to have a wider protection scope and the function of tripping the traction network in conjunction with the power grid to cut off the transmission of power flow when the power grid is faulty. This can be perfectly solved by arranging transmission line protection in the power grid and arranging hierarchical protection in the traction network.

[0006] The second problem is the impact of ride-through power flow on the power grid and the problem of metering. When the ride-through power flow returns to the power grid, it is equivalent to the traction substation generating power. If the backfeed power flow is metered backwards, i.e., treated as power generation and offset with the power consumption of another traction substation, users will not suffer economic loss. If the ride-through power flow is not metered or is metered forwards when it returns to the power grid, it will cause economic loss to users. In such cases, it is necessary to study how bilateral power supply can reduce the ride-through power flow or how to utilize the ride-through power flow to properly exert the advantages of bilateral power supply while reducing the impact on the power grid and users and improving the efficiency of power consumption.

[0007] For the ride-through power flow, the prior art has proposed several suppression methods. One is to reduce the balancing current by connecting a reactor in series with the secondary side of the traction transformer in the traction substation, as in the Chinese patent "Electric Railway Bilateral Power Supply System" (license publication number: CN103552488B), the disadvantages of which are that the reactor required is relatively large, and the power factor of the train needs to be adjusted to a leading power factor, otherwise it may affect the supply voltage and supply capacity. Theoretically, the ride-through power flow and balancing current cannot be made zero unless the impedance of the secondary side of the traction transformer becomes infinite.

[0008] Setting aside the current research into the suppression technology of the ride-through power flow of bilateral power supply, we have changed our thinking and proposed a smart traction substation and its power flow control method to realize in-phase bilateral through power supply of electric railways, eliminate electrical phase splitting, and eliminate dead sections. In addition, by using the ride-through power flow of bilateral power supply returning to the power grid and the regenerative energy caused by the braking of the electric locomotive in the traction network as the power flow to be generated, the power flow to be generated returning to the power grid can be made to meet the preset requirements, for example, zero, and the excess negative phase can be compensated for, so that the negative phase meets the national standard requirements. Summary of the Invention [Problem to be solved by the invention]

[0009] The objective of the present invention is to provide a smart traction substation and a power flow control method thereof, which (1) enables the power flow of a traction substation to be controlled, (2) utilizes the generated power flow returning to the power grid from the traction network OCS using bilateral power supply and the generated power flow caused by braking of an electric locomotive in the traction network to ensure that the generated power flow returning to the power grid meets the preset requirements, and (3) effectively solves the technical problems of compensating for excess negative phase and ensuring that the negative phase meets the 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-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 the power amount 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 returning to the traction substation from the AC bilateral power supply traction network OCS, 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 unit 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 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 an AC side is connected to three-phase buses a, b, and c of a traction substation power distribution system, respectively; The positive and negative poles of the DC sides of the converter unit PPC, converter unit TPC, converter unit DPC and energy storage unit 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 unit TPC, a converter unit PPC, a converter unit DPC, and an energy storage unit ES.

[0016] The present invention also provides The voltage transformer PT detects a voltage UT of a traction bus TSB, and the current transformers CT1 and CT2 detect 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 back to the traction substation, so that the generated power flow back to the power grid meets the preset requirements.

[0017] 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 from the traction network OCS1, the traction network OCS2 back to the traction substation, so that the generated power flow back 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, in this case, it controls the converter devices TPC and DPC of the power flow control device PCD to operate and supply power to the three-phase buses a, b, and c of the power distribution system, or controls the energy storage device ES of the converter device TPC to charge, 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, so as to meet the preset requirement, and also controls the converter device PPC of the power flow control device PCD to be on standby; When P1+P2>0, the controller CC determines that the feeder F1 and the feeder F2 meet the traction operation condition, 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 supply power to the traction bus TSB by the converter device TPC, 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 standby. Effect 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 caused by the braking of electric locomotives in the traction network can all be used as the generated power flow, so that the generated power flow returning to the power grid can be made 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 impacts of ride-through power flow on the power grid and users, and fully utilizing 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 the regenerative braking energy, and reducing the amount of regenerative power and electrical energy returned to the power grid under normal conditions to zero. 4. The power flow control device can be connected to the traction substation's energy storage device and distribution system to supply power, and in addition to utilizing the ride-through power flow, it can also utilize surplus regenerative braking electrical energy. 5. By multiplexing the in-phase power supply of the traction substation and the generation power flow utilization equipment, equipment duplication and investment can be reduced. 6. The technology is advanced, reliable and easy to implement. [Brief description 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 embodiments of the present invention but are not intended to limit the embodiments of the present invention.

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

[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 drawings and specific embodiments.

[0023] Example 1 As shown in FIG. 1, the present 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 traction transformer TT has a primary side connected to the U-phase and V-phase of a three-phase power grid, one end of the 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 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 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 AC bilateral power supply traction network OCS to the traction substation, so that the generated power flow returning to the power grid meets the preset requirements.

[0024] In this embodiment, by using the power flow control device PCD to perform negative phase compensation for the traction transformer TT and ensuring that the negative phase meets the national standard requirements, the smart traction substation of this embodiment realizes in-phase power supply and eliminates electrical phase splitting at the substation, and by using bilateral power supply for the traction network OCS, the electrical phase splitting in the section between the two substations is eliminated, 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 FIG. 1, if the power flow from the smart traction substation back to the power grid is the power generation 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 the smart traction substation to the power grid as the power generation power flow. In fact, the regenerative power flow generated when the locomotive brakes also flows from the smart substation to the power grid, or the regenerative power flow generated when the locomotive brakes also flows from the smart substation to the power grid, or the regenerative power flow generated when the locomotive brakes. When the power flow is not completely absorbed by the accompanying traction locomotive and the excess regenerative power flow also flows into the power grid, the regenerative power flow or the excess regenerative power flow flowing from the smart substation to the power grid is superimposed with the ride-through power flow and treated as the total generated power flow by the controller CC, and 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 certain range or to make the generated power flow returning to the power grid zero. In the specific smart traction substation shown in FIG. 1, when the power flow of the smart traction substation is put into a traction state, a ride-through power flow occurs in the traction network OCS due to the use of bilateral power supply, and 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 a 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] In this embodiment, the power flow returning to the smart traction substation is utilized without changing the power supply structure of the power grid to the railway, effectively eliminating the adverse effects of the ride-through power flow and regenerative power flow caused by bilateral power supply on the power grid and users, and fully exerting the advantages of bilateral power supply. In addition, in this embodiment, the power flow control device PCD is used to perform reverse phase compensation and utilization of the power flow generated, thereby multiplexing the in-phase power supply and the power flow utilization device of the smart traction substation, effectively reducing equipment duplication and investment.

[0027] In addition, although it is described in the background art that it is necessary 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, that is, this embodiment may or may not adopt this measure. The core of this embodiment is to utilize the generated power flow returning to the substation, and by using bilateral power supply, ride-through power flow is always present, and this embodiment focuses on responding to the result of ride-through power flow rather than suppressing the occurrence 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, 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, so that the power supply arm is extended and the traction train among the accompanying trains can absorb the regenerative power flow of the braking train with a higher probability, thereby increasing the direct utilization rate of the regenerative braking energy, and finally greatly reducing the regenerative power flow returning to the power grid, even to zero. In order to facilitate maintenance, this embodiment may also install an electrical section in the traction network OCS of the substation, that is, install an electrical section between the traction network OCS1 and the traction network OCS2. The installation of the electrical section is used in combination with the sectioning measurement control protection technology to prevent the train from being out of power, and facilitate 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 a controller CC, and a control terminal of the controller CC is connected to a control terminal 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, and 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 the 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 units PPC, TPC, DPC and energy storage unit 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 is 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 a neutral line (i.e., the N line in FIG. 1), or may be connected to a 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 a converter unit TPC, a converter unit PPC, a converter unit DPC and an energy storage unit 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, and after judgment and control, the ride-through power flow of bilateral power supply returning to the power grid and the regenerative power caused by the braking of the electric locomotive in the traction network can all be used as the generated power flow, so that the generated power flow returning to the power grid can be made zero or meet the requirements, and excessive negative phase can be compensated for so that the negative phase meets the 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 impacts of ride-through power flow on the power grid and users, and fully utilizing 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 the regenerative braking energy, and reducing the amount of regenerative power and electrical energy returned to the power grid under normal conditions to zero. 4. The power flow control device can be connected to the traction substation's energy storage device and distribution system to supply power, and in addition to utilizing the ride-through power flow, it can also utilize surplus regenerative braking electrical energy. 5. By multiplexing the in-phase power supply of the traction substation and the generation power flow utilization equipment, 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, which includes the following steps:

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

[0038] Step S200: The controller CC calculates the active power flows that the traction bus TSB supplies to the traction networks OCS1 and OCS2 via the feeders F1 and F2, respectively, from the detected voltage of the traction bus TSB and the currents of the feeders F1 and F2, and the active power flows that flow into the traction networks OCS1 and OCS2 are positive, and the active power flow that flows into 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 further comprises: 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 from the traction network OCS1, the traction network OCS2 back to the traction substation, so that the generated power flow back to the power grid meets the preset requirements.

[0041] Preferably, the method further 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, in this case, it controls the converter devices TPC and DPC of the power flow control device PCD to operate and supply power to the three-phase buses a, b, and c of the power distribution system, or controls the energy storage device ES of the converter device TPC to charge, 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, so as to meet the preset requirement, and also controls the converter device PPC of the power flow control device PCD to be on standby; When P1+P2>0, the controller CC determines that the feeder F1 and the feeder F2 meet the traction operation condition, 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 supply power to the traction bus TSB by the converter device TPC, 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 standby.

[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 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 to the traction substation from the AC bilateral power supply traction network OCS by supplying power to or storing energy in a power distribution system, so that the generated power flow returning to the power grid meets the preset 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 unit 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 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 an 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, characterized in that 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 on the DC side are connected to the positive bus PB and the negative bus NB, respectively.

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

5. 5. The smart traction substation according to claim 3 or 4, characterized in that the feeders F include 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.

6. The smart traction substation according to claim 5, characterized in that: 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 a smart traction substation as claimed in claim 6, comprising: the voltage transformer PT detecting a voltage UT of a traction bus TSB, and the current transformers CT1 and CT2 detecting currents of 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 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; The power flow control method according to claim 7, characterized in that the controller CC controls the converter device TPC and the converter device 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 back to the traction substation, so that the generated power flow back to the power grid meets the preset requirements.

9. If P1+P2<0, the controller CC determines that the feeder F1 and the feeder F2 have returned the generated power flow to the power grid, in this case, it controls the converter device TPC, the converter device DPC of the power flow control device PCD to operate and supply power to the three-phase bus a, the bus b, and the bus c of the power distribution system, or controls the energy storage device ES of the converter device TPC to charge, 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, so as to meet the preset requirement, and also controls the converter device PPC of the power flow control device PCD to be on standby; When P1+P2>0, the controller CC determines that the feeder F1 and the feeder F2 meet the traction operation condition, 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 to supply power to the traction bus TSB by the converter device TPC, 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, characterized in that, 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 be on standby.

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