An energy interconnection and conversion system and control method for connecting new energy power plants and railway traction power supply systems.

Abstract

This invention belongs to the field of AC electrified railway traction power supply technology, specifically relating to an energy interconnection and conversion system and control method for energy interconnection between a new energy power station and a railway traction power supply system. This method provides an energy conversion topology and energy interconnection control method for energy interconnection between a new energy power station and a railway traction power supply system. It enables the new energy power station to supply power to the railway traction power supply system, achieving both the provision of clean energy from large-capacity new energy sources to the railway traction power supply system, improving the green energy consumption level of railway traction power supply, and solving the problem of insufficient grid absorption capacity commonly faced by new energy power stations. Simultaneously, the regenerative braking energy of the railway traction load can be fed back to the new energy power station with good power quality, solving the problem of poor power quality and lack of economic benefits when the remaining new energy (surplus electricity) and regenerative braking energy after traction load absorption are fed back to the grid through existing traction substations.

Description

Technical Field

[0001] This invention belongs to the field of AC electrified railway traction power supply technology, specifically relating to an energy interconnection and conversion system and control method for energy between a new energy power station and a railway traction power supply system. Background Technology

[0002] With the expansion of new energy power plant construction, the grid's carrying capacity is increasingly being tested, and in many regions, the load supplied by the grid cannot fully absorb new energy. In this context, there is an urgent need to explore new measures to improve the absorption of new energy by energy-intensive industries and address the problem of insufficient grid-side new energy absorption capacity. Electrified railways play a crucial role in the economic and social development of countries worldwide. Currently, there is considerable research and exploration into the application of new energy power generation technology in the rail transit sector, with distributed photovoltaic and energy storage connected to electrified railway traction power supply systems in the demonstration application stage. Publicly reported applications of new energy in electrified railways, especially those connected to railway traction power supply systems, are mostly built along the railway lines, such as on station rooftops, station grounds, and railway slopes. The limited area for new energy construction along railway lines results in generally small installed capacities, typically ranging from tens of kW to several MW. Therefore, railway traction power supply systems often face the problem of limited new energy construction capacity.

[0003] Secondly, the railway traction power supply system is single-phase, requiring traction transformers to convert three-phase electricity into one or two single-phase circuits. Therefore, the energy conversion between the grid side and the traction side is asymmetrical. Under the condition that the railway traction load is a single-phase load, a large negative sequence current will be generated on the grid side, increasing the voltage imbalance on the grid side. Therefore, the large amount of regenerative braking energy generated by electric locomotives or EMUs is fed back to the grid as asymmetrical energy, which is undesirable to the grid. Thus, the fed-back regenerative braking energy has no economic value.

[0004] New energy sources along railway lines are generally connected to the traction busbars of railway traction substations and consumed by the traction load. The remaining new energy after the traction load is consumed is referred to as surplus electricity. This surplus electricity is either stored in expensive energy storage systems or fed back to the grid. However, for the reasons mentioned above, the surplus electricity fed back to the grid will also generate a large negative sequence current on the grid side, and therefore does not generate economic value.

[0005] In the prior art, for example, Chinese patent number CN201810934439.X discloses an invention patent for an off-grid traction power supply system based on battery energy storage and multi-energy complementarity. Figure 1a As shown, a three-phase wind power generation system, a three-phase photovoltaic power generation system, and an energy storage unit supply power to the three-phase AC bus, and then a traction transformer connected to the three-phase AC bus supplies power to the traction network. Similarly, patent number CN201621211746.8 discloses a railway traction power supply system based on photovoltaic power generation, such as... Figure 1b As shown, patent number CN201621212838.8 discloses a high-efficiency and energy-saving railway traction power supply system, such as... Figure 1c As shown, patent number CN201720123338.5 discloses a high-speed railway traction power supply system incorporating photovoltaic power, such as... Figure 1d As shown, the aforementioned patent only applies to scenarios where three-phase inverters are connected to the traction network via transformers with different wiring configurations (Vv, Ynd11, and Dyn11). The three-phase power supplies used for new energy access in the aforementioned patent claims all require voltage transformation from the two traction busbars of the traction substation through different types of transformers to maintain their operation. Therefore, the capacity of this three-phase power supply is much smaller than the capacity of the traditional power grid, resulting in a smaller capacity of accessible new energy sources. Furthermore, the small capacity of the three-phase power supply significantly reduces the system's operational stability.

[0006] Patent number CN201820581706.5 discloses a traction photovoltaic power generation system for brake energy recovery, such as... Figure 2 As shown, patent number CN201820581713.5 discloses a railway photovoltaic energy storage system for regenerative braking energy recovery, patent number CN201721334804.0 discloses a multi-energy complementary grid-connected system applied to electrified railways, and papers such as "Analysis of Harmonic Interaction Influence and Adaptability of Photovoltaic Access to Traction Power Supply System" and "Back-to-Back Photovoltaic Power Generation System and Control Strategy for Electrified Railways" all disclose or propose different forms of photovoltaic or wind-solar-storage power generation systems applied to traction substations of electrified railways. All of these require two transformers connected to an AC-DC-AC converter, with the DC end of the AC-DC-AC converter connected to the new energy power generation and energy storage systems. Since the photovoltaic systems in these schemes can only be connected to the DC end of the AC-DC-AC converter, they are suitable for small-capacity distributed new energy access to railway traction power supply systems near traction substations, but not for large-capacity, especially long-distance, new energy access to railway traction power supply systems.

[0007] In the application of large-capacity new energy sources in electrified railway traction power supply systems, existing technologies have the following main drawbacks:

[0008] 1. In existing technical solutions applied to electrified railway traction power supply systems, new energy sources are mostly connected to the traction side of the traction power supply, and are connected through the DC side of the AC-DC-AC converter. Due to the insufficient photovoltaic construction sites along the railway line, the capacity of new energy sources connected to the railway traction power supply system is relatively small, which is not suitable for large-capacity, especially long-distance, new energy sources connected to the railway traction power supply system.

[0009] 2. In existing technical solutions applied to electrified railway traction power supply systems, some scholars have proposed a scheme to connect new energy sources through three-phase power. However, the three-phase power supply in these schemes requires voltage transformation from two traction busbars at the traction substation by a transformer. Therefore, the capacity of this three-phase power supply is much smaller than that of the traditional power grid, resulting in a smaller capacity of new energy sources that can be connected. Furthermore, the small capacity of the three-phase power supply significantly reduces the stability of the system operation.

[0010] 3. Regarding the feedback of surplus electricity and regenerative braking energy to the grid, both of the above-mentioned schemes involve feeding the remaining renewable energy or regenerative braking energy after the traction load has been absorbed back to the grid through the traction transformers in the traction substation. Because the traction transformers in railway traction substations are asymmetrical transformers, the energy fed back to the grid will generate a large amount of negative sequence current, exacerbating the voltage imbalance on the grid side and adversely affecting the power quality. Furthermore, due to the electricity billing principles on the grid side of the traction substation, the energy fed back to the grid is not included in the electricity billing calculation; therefore, feeding renewable energy back to the grid through the traction substation generally does not generate economic benefits.

[0011] Therefore, in view of the above three technical shortcomings or deficiencies, there is an urgent need for an energy interconnection and conversion system and control method that can enable large-capacity new energy to be connected to the railway traction power supply system, and the surplus power to be fed into the grid without deteriorating the power quality on the grid side, and even generate certain economic benefits. Summary of the Invention

[0012] The purpose of this invention is to provide an energy interconnection and conversion system and control method for connecting a new energy power plant and a railway traction power supply system. The new energy power plant, as a new energy source, supplies power to the railway traction power supply system through the energy interconnection and power conversion system, enabling large-capacity new energy to provide clean electricity to the railway traction power supply system and improving the greening level of energy use in railway traction power supply. Furthermore, surplus electricity can be improved in power quality through three-phase symmetrical conversion and fed back to the grid from the new energy power plant, ensuring both grid-side power quality and generating revenue from surplus electricity fed into the grid.

[0013] The specific technical solution adopted by this invention is as follows:

[0014] An energy interconnection and conversion system for new energy power plants and railway traction power supply systems includes a main circuit and a control circuit.

[0015] The main circuit connects the existing new energy power station and the railway traction power supply system; wherein, the main circuit connects to the low-voltage end of the three-phase grid-connected transformer of the existing new energy power station, that is, the new energy generator set side, without requiring any modification to the high-voltage grid-connected side of the existing new energy power station; at the same time, the main circuit connects to the two traction bus ends of the railway traction substation.

[0016] The control circuit collects information from new energy power plants and railway traction substations. The information from new energy power plants mainly includes the output signals of the voltage transformers and current transformers on the low-voltage side of the three-phase grid-connected transformers, while the information from railway traction substations mainly includes the voltage and current signals on the traction load side.

[0017] A control method for an energy interconnection and conversion system between a new energy power plant and a railway traction power supply system includes the following steps:

[0018] Step 1: Collect the output signals of the voltage transformer and current transformer of the new energy power station, and calculate the new energy power generation P. ng The calculated new energy power generation P ng The control circuit of the energy interconnection and conversion system is transmitted via wired or wireless transmission.

[0019] Step 2: Collect the output signals of the voltage transformer and current transformer of phase a of the railway traction substation, and calculate the traction load power P of phase a. ra A positive value indicates that the traction load absorbs electrical energy and the train is in traction mode; a negative value indicates that the traction load generates electrical energy and the train is in regenerative braking mode; the same applies below.

[0020] Collect the output signals of the voltage transformer and current transformer of phase b in the railway traction substation, and calculate the traction load power P of phase b. rb ;

[0021] Step 3: Identify the traction load conditions for the traction load power of phase a and phase b respectively. When the load power is greater than 0, it is considered to be the traction condition; when the load power is less than 0, it is considered to be the regenerative braking condition.

[0022] Step 4: Generate two grid-connected unit power commands for the traction load conditions of phase a and phase b respectively:

[0023] When the traction load of phase a is traction condition P ra >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the single-phase grid-connected unit of phase a is P×a=Min (P ra P ng S Cona S Reca ); where S Cona and S Reca Converter C ona and three-phase rectifier R ec a is the rated capacity; Min() is the minimum value function, P×a greater than 0 indicates that electrical energy is supplied to the traction load, the same below;

[0024] When the traction load of phase a is in regenerative braking condition P raWhen <0, the output power command of the single-phase grid-connected unit of phase a is P×a=Max(P ra -S Cona -S Reca ); where S Cona and S Reca Converter C ona and three-phase rectifier R eca Rated capacity; Max() is the maximum value function; P×a less than 0 indicates that electrical energy is absorbed from the traction load, the same below;

[0025] When the traction load of phase b is the traction condition P rb >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the b-phase single-phase grid-connected unit is P×b=Min (P rb P ng S Conb S Recb ); where S Conb and S Recb Converter C onb The rated capacity of the three-phase rectifier Recb;

[0026] When the traction load of phase b is in regenerative braking condition P rb When <0, the output power command of the b-phase single-phase grid-connected unit is P×b=Max(P rb -S Conb -S Recb ); where S Conb and S Recb Converter C onb and three-phase rectifier R ecb Rated capacity;

[0027] Step 5: Based on the power commands from the two grid-connected units, perform converter C... ona and converter C onb The closed-loop control typically employs a dual closed-loop control system with an outer voltage or power loop and an inner current loop to achieve operation according to the aforementioned power command; simultaneously, the two single-phase rectifiers R eca and R ecb Dual closed-loop control, consisting of an outer voltage loop and an inner current loop, is implemented to stabilize DC voltage and achieve bidirectional power transmission.

[0028] The technical effects achieved by this invention are as follows:

[0029] This invention solves the problem of insufficient photovoltaic construction sites along railway stations, resulting in limited renewable energy capacity for railway traction power supply systems. Existing methods for constructing renewable energy power generation systems around railway stations are limited by site size, with renewable energy, such as photovoltaic power generation, generally not exceeding 6MW. This invention utilizes existing renewable energy power plants as the renewable energy source, no longer limiting itself to constructing renewable energy systems around railway stations. Therefore, it can provide tens or even hundreds of MW of renewable energy to the railway traction power supply system, significantly increasing the renewable energy capacity.

[0030] This invention solves the problem of large negative sequence currents caused by the feedback of surplus electricity from new energy sources and regenerative braking energy to the power grid through railway traction substations, which exacerbates voltage imbalance on the grid side. This patent uses a three-phase rectifier (Reca and Recb) to perform symmetrical energy conversion of surplus electricity or regenerative braking energy, which eliminates the negative sequence component of the grid-side current, thus avoiding any adverse impact on the voltage imbalance on the grid side.

[0031] In this invention, the feedback of surplus electricity from renewable energy sources and regenerative braking energy to the power grid can generate economic benefits. This patent feeds surplus electricity or regenerative braking energy back to the power grid through existing renewable energy power plants, avoiding feedback from traction substations. Since the grid-connected electricity from renewable energy power plants is profitable, the proposed solution of feeding surplus electricity from renewable energy sources and regenerative braking energy back to the power grid through existing renewable energy power plants can also generate economic benefits. Attached Figure Description

[0032] Figure 1 is a schematic diagram of the prior art;

[0033] Figure 2 This is a schematic diagram of existing technology;

[0034] Figure 3 This is a connection diagram of the energy interconnection and conversion system of the present invention;

[0035] Figure 4 This is the main circuit structure of the energy interconnection and conversion system of the present invention;

[0036] Figure 5 It is a control system block diagram. Detailed Implementation

[0037] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0038] like Figures 3-5 As shown, an energy interconnection and conversion system for new energy power plants and railway traction power supply systems, such as... Figure 3 As shown, it includes the main circuit and the control circuit;

[0039] The main circuit connects the existing new energy power station and the railway traction power supply system; wherein, the main circuit connects to the low-voltage end of the three-phase grid-connected transformer of the existing new energy power station, that is, the new energy generator set side, without requiring any modification to the high-voltage grid-connected side of the existing new energy power station; at the same time, the main circuit connects to the two traction bus ends of the railway traction substation.

[0040] The control circuit collects information from new energy power plants and railway traction substations. The information from new energy power plants mainly includes the output signals of the voltage transformers and current transformers on the low-voltage side of the three-phase grid-connected transformers, while the information from railway traction substations mainly includes the voltage and current signals on the traction load side.

[0041] Preferably, the main circuit includes a three-phase incoming line unit, a three-phase transmission line, a three-phase rectifier unit, a phase a single-phase grid-connected unit, and a phase b single-phase grid-connected unit, such as... Figure 4 As shown; among them, the three-phase incoming line unit is on the side of the new energy power station, and the three-phase rectifier unit, the a-phase single-phase grid-connected unit, and the b-phase single-phase grid-connected unit are on the side of the railway traction substation.

[0042] Preferably, the three-phase incoming line unit includes a circuit breaker and a current transformer, with its input end connected to the low-voltage end of the three-phase grid-connected transformer of the existing new energy power station, and its output end connected to the three-phase transmission line.

[0043] Preferably, the three-phase transmission line can be a three-phase overhead transmission line or a three-phase cable transmission line, enabling the long-distance transmission of electrical energy from the new energy power station to the railway traction substation.

[0044] Preferably, the three-phase rectifier unit includes an input switch, a voltage transformer, a current transformer, and two three-phase rectifiers R. eca and R ecb The input end of the three-phase rectifier unit is connected to the three-phase transmission line, and the output end is connected to the DC bus to realize the conversion of electrical energy between the three-phase AC side and the DC side, and to realize the bidirectional transmission of electrical energy. Among them, the two three-phase rectifiers are connected in parallel on the AC side, and the DC side is connected to a set of DC buses respectively.

[0045] Preferably, the single-phase grid-connected unit of phase a includes circuit breaker II, voltage transformer PTa, current transformer CTa, transformer TTa, and converter C. ona The DC side of the single-phase grid-connected unit is connected to a set of DC buses, and the AC side is connected to the phase a traction bus of the railway traction substation; this realizes the conversion of electrical energy between the DC bus and the phase a traction bus, and achieves bidirectional transmission of electrical energy.

[0046] Preferably, the b-phase single-phase grid-connected unit includes a circuit breaker, a voltage transformer PTb, a current transformer CTb, a transformer TTb, and a converter C. onb The DC side of the b-phase single-phase grid-connected unit is connected to another set of DC buses, and the AC side is connected to the b-phase traction bus of the railway traction substation, realizing the power conversion between the DC bus and the b-phase traction bus and realizing bidirectional power transmission.

[0047] Preferably, the two sets of DC buses can also be connected to one or both of a new energy power generation system and an energy storage system; wherein, the new energy power generation system can be arranged along the railway line and in surrounding stations.

[0048] A control method for an energy interconnection and conversion system between a new energy power plant and a railway traction power supply system includes the following steps:

[0049] Step 1: Collect the output signals of the voltage transformer and current transformer of the new energy power station, and calculate the new energy power generation P. ng The calculated new energy power generation P ng The control circuit of the energy interconnection and conversion system is transmitted via wired or wireless transmission.

[0050] Step 2: Collect the output signals of the voltage transformer and current transformer of phase a of the railway traction substation, and calculate the traction load power P of phase a. ra A positive value indicates that the traction load absorbs electrical energy and the train is in traction mode; a negative value indicates that the traction load generates electrical energy and the train is in regenerative braking mode; the same applies below.

[0051] Collect the output signals of the voltage transformer and current transformer of phase b in the railway traction substation, and calculate the traction load power P of phase b. rb ;

[0052] Step 3: Identify the traction load conditions for the traction load power of phase a and phase b respectively. When the load power is greater than 0, it is considered to be the traction condition; when the load power is less than 0, it is considered to be the regenerative braking condition.

[0053] Step 4: Generate two grid-connected unit power commands for the traction load conditions of phase a and phase b respectively:

[0054] When the traction load of phase a is traction condition P ra >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the single-phase grid-connected unit of phase a is P×a=Min (P ra P ng S Cona S Reca ); where S Cona and S Reca Converter Cona and three-phase rectifier R ec a is the rated capacity; Min() is the minimum value function, P×a greater than 0 indicates that electrical energy is supplied to the traction load, the same below;

[0055] When the traction load of phase a is in regenerative braking condition P ra When <0, the output power command of the single-phase grid-connected unit of phase a is P×a=Max(P ra -S Cona -S Reca ); where S Cona and S Reca Converter C ona and three-phase rectifier R eca Rated capacity; Max() is the maximum value function; P×a less than 0 indicates that electrical energy is absorbed from the traction load, the same below;

[0056] When the traction load of phase b is the traction condition P rb >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the b-phase single-phase grid-connected unit is P×b=Min (P rb P ng S Conb S Recb ); where S Conb and S Recb Converter C onb The rated capacity of the three-phase rectifier Recb;

[0057] When the traction load of phase b is in regenerative braking condition P rb When <0, the output power command of the b-phase single-phase grid-connected unit is P×b=Max(P rb -S Conb -S Recb ); where S Conb and S Recb Converter C onb and three-phase rectifier R ecb Rated capacity;

[0058] Step 5: Based on the power commands from the two grid-connected units, perform converter C... ona and converter C onb The closed-loop control typically employs a dual closed-loop control system with an outer voltage or power loop and an inner current loop to achieve operation according to the aforementioned power command; simultaneously, the two single-phase rectifiers R eca and R ecb The system employs dual closed-loop control with an outer voltage loop and an inner current loop to stabilize the DC voltage and achieve unity power factor operation on the AC side. This allows for bidirectional power transmission of the system based on the operating states of the two converters.

[0059] The working principle of this invention is as follows: The energy interconnection and conversion system structure of this invention connects the renewable energy power station and the railway traction busbar, enabling direct green electricity supply from the large-capacity renewable energy power station to the railway traction load. The energy interconnection and conversion system includes a three-phase incoming line unit, a three-phase transmission line, a three-phase rectifier unit, an a-phase single-phase grid-connected unit, and a b-phase single-phase grid-connected unit. The three-phase incoming line unit is located on the renewable energy power station side, connecting to the low-voltage end of the existing renewable energy power station's three-phase grid-connected transformer, i.e., the renewable energy generator set side. The three-phase rectifier unit, the a-phase single-phase grid-connected unit, and the b-phase single-phase grid-connected unit are located on the railway traction substation side, with two single-phase grid-connected units respectively connecting to the two traction buses of the railway traction substation.

[0060] This invention discloses a control method for an energy interconnection and conversion system. This method comprehensively utilizes the power generation status and traction load status of the renewable energy power station to achieve real-time control of energy interconnection between the renewable energy power station and railway traction power supply. It calculates the renewable energy power generation and the traction load power of phases a and b of the traction substation. Then, based on the magnitude of the traction load power, it identifies whether the traction load is in traction or regenerative braking mode. Next, based on the output power status of the renewable energy power station, the traction load mode, and the equipment capacity, it calculates the output power of the single-phase grid-connected converters for phases a and b, respectively. This allows the photovoltaic power from the existing renewable energy power station to be absorbed by the traction load when there is traction load and it is in traction mode, and to be fed back to the grid when there is no traction load. Furthermore, when the traction load is in regenerative braking mode, the regenerative braking energy can also be fed back to the grid through the renewable energy power station.

[0061] This invention solves the problem of insufficient photovoltaic construction sites along railway stations, resulting in limited renewable energy capacity for railway traction power supply systems. Existing methods for constructing renewable energy power generation systems around railway stations are limited by site size, with renewable energy, such as photovoltaic power generation, generally not exceeding 6MW. This invention utilizes existing renewable energy power plants as the renewable energy source, no longer limiting itself to constructing renewable energy systems around railway stations. Therefore, it can provide tens or even hundreds of MW of renewable energy to the railway traction power supply system, significantly increasing the renewable energy capacity.

[0062] This invention solves the problem of large negative sequence currents caused by the feedback of surplus electricity from new energy sources and regenerative braking energy to the power grid through railway traction substations, which exacerbates voltage imbalance on the grid side. This patent uses a three-phase rectifier (Reca and Recb) to perform symmetrical energy conversion of surplus electricity or regenerative braking energy, which eliminates the negative sequence component of the grid-side current, thus avoiding any adverse impact on the voltage imbalance on the grid side.

[0063] In this invention, the feedback of surplus electricity from renewable energy sources and regenerative braking energy to the power grid can generate economic benefits. This patent feeds surplus electricity or regenerative braking energy back to the power grid through existing renewable energy power plants, avoiding feedback from traction substations. Since the grid-connected electricity from renewable energy power plants is profitable, the proposed solution of feeding surplus electricity from renewable energy sources and regenerative braking energy back to the power grid through existing renewable energy power plants can also generate economic benefits.

[0064] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. An energy interconnection and conversion system for new energy power plants and railway traction power supply systems, characterized in that: Includes the main circuit and the control circuit; The main circuit is connected to the low-voltage end of the three-phase grid-connected transformer of the new energy power station, i.e., the new energy generator set side; at the same time, the main circuit is connected to the two traction bus ends of the railway traction substation. The main circuit includes a three-phase rectifier unit, a phase a single-phase grid-connected unit, and a phase b single-phase grid-connected unit; the three-phase rectifier unit has two three-phase rectifiers R. eca and R ecb The AC side is connected in parallel, and the DC side is connected to a set of DC buses respectively; The converter C of the single-phase grid-connected unit of phase a ona The DC side is connected to a set of DC buses, and the AC side is connected to the a-phase traction bus of the railway traction substation. The converter C of the b-phase single-phase grid-connected unit onb The DC side is connected to another set of DC buses, and the AC side is connected to the b-phase traction bus of the railway traction substation. The control method for an energy interconnection and conversion system includes the following steps: Step 1: Collect the output signals of the voltage transformer and current transformer of the new energy power station, and calculate the new energy power generation P. ng The calculated new energy power generation P ng The control circuit of the energy interconnection and conversion system is transmitted via wired or wireless transmission. Step 2: Collect the output signals of the voltage transformer and current transformer of phase a of the railway traction substation, and calculate the traction load power P of phase a. ra A positive value indicates that the traction load absorbs electrical energy and the train is in traction mode; a negative value indicates that the traction load generates electrical energy and the train is in regenerative braking mode; the same applies below. Collect the output signals of the voltage transformer and current transformer of phase b in the railway traction substation, and calculate the traction load power P of phase b. rb ; Step 3: Identify the traction load conditions for the traction load power of phase a and phase b respectively. When the load power is greater than 0, it is considered to be the traction condition; when the load power is less than 0, it is considered to be the regenerative braking condition. Step 4: Generate two grid-connected unit power commands for the traction load conditions of phase a and phase b respectively: When the traction load of phase a is traction condition P ra >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the single-phase grid-connected unit of phase a is... (P) ra P ng S Cona S Reca ); where S Cona and S Reca Converter C ona and three-phase rectifier R ec The rated capacity of a; Min() is the minimum value function. A value greater than 0 indicates that electrical energy is supplied to the traction load, and the same applies below; When the traction load of phase a is in regenerative braking condition P ra When <0, the output power command of the a-phase single-phase grid-connected unit is... (P) ra -S Cona -S Reca ); where S Cona and S Reca Converter C ona and three-phase rectifier R eca The rated capacity; Max() is the function to retrieve the maximum value; A value less than 0 indicates that electrical energy is absorbed from the traction load, and the same applies below; When the traction load of phase b is the traction condition P rb >0, and the power generation of new energy sources P ng When the value is greater than 0, the output power command of the b-phase single-phase grid-connected unit is... (P) rb P ng S Conb S Recb ); where S Conb and S Recb Converter C onb The rated capacity of the three-phase rectifier Recb; When the traction load of phase b is in regenerative braking condition P rb When <0, the output power command of the b-phase single-phase grid-connected unit is... (P) rb -S Conb -S Recb ); where S Conb and S Recb Converter C onb and three-phase rectifier R ecb Rated capacity; Step 5: Based on the power commands from the two grid-connected units, perform converter C... ona and converter C onb The closed-loop control typically employs a dual closed-loop control system with an outer voltage or power loop and an inner current loop to achieve operation according to the aforementioned power command; simultaneously, the two single-phase rectifiers R eca and R ecb Dual closed-loop control, consisting of an outer voltage loop and an inner current loop, is implemented to stabilize DC voltage and achieve bidirectional power transmission.

2. The energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 1, characterized in that: The main circuit includes a three-phase incoming line unit, a three-phase transmission line, a three-phase rectifier unit, an a-phase single-phase grid-connected unit, and a b-phase single-phase grid-connected unit. The three-phase incoming line unit is located on the side of the new energy power station, while the three-phase rectifier unit, the a-phase single-phase grid-connected unit, and the b-phase single-phase grid-connected unit are located on the side of the railway traction substation.

3. The energy interconnection and conversion system for new energy power plants and railway traction power supply systems according to claim 2, characterized in that: The three-phase incoming line unit includes a circuit breaker and a current transformer. Its input end is connected to the low-voltage end of the three-phase grid-connected transformer of the new energy power station, and its output end is connected to the three-phase transmission line.

4. The energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 3, characterized in that: The three-phase transmission line is either a three-phase overhead transmission line or a three-phase cable transmission line, which enables the long-distance transmission of electrical energy from the new energy power plant to the railway traction substation.

5. The energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 4, characterized in that: The three-phase rectifier unit includes an input switch, a voltage transformer, a current transformer, and two three-phase rectifiers R. eca and R ecb The input end of the three-phase rectifier unit is connected to the three-phase transmission line, and the output end is connected to the DC bus to realize the conversion of electrical energy between the three-phase AC side and the DC side, and to realize the bidirectional transmission of electrical energy. Among them, the two three-phase rectifiers are connected in parallel on the AC side, and the DC side is connected to a set of DC buses respectively.

6. The energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 5, characterized in that: The single-phase grid-connected unit of phase a includes circuit breaker II, voltage transformer PTa, current transformer CTa, transformer TTa, and converter C. ona The DC side of the single-phase grid-connected unit is connected to a set of DC buses, and the AC side is connected to the phase a traction bus of the railway traction substation; this realizes the conversion of electrical energy between the DC bus and the phase a traction bus, and achieves bidirectional transmission of electrical energy.

7. An energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 6, characterized in that: The b-phase single-phase grid-connected unit includes circuit breaker III, voltage transformer PTb, current transformer CTb, transformer TTb, and converter C. onb The DC side of the b-phase single-phase grid-connected unit is connected to another set of DC buses, and the AC side is connected to the b-phase traction bus of the railway traction substation, realizing the power conversion between the DC bus and the b-phase traction bus and realizing bidirectional power transmission.

8. The energy interconnection and conversion system for a new energy power plant and a railway traction power supply system according to claim 7, characterized in that: The two sets of DC buses can also be connected to one or both of the new energy power generation system and the energy storage system; among them, the new energy power generation system is arranged along the railway line and in the surrounding stations.

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