A power flow controller between transformers

Abstract

This invention discloses a power flow controller (TPFC) for multiple transformers, applied to power flow regulation and power quality management among multiple transformers. The controller includes two ports, a first transformer, a second transformer, three controllable converters, a DC bus, a coupling module, and a comprehensive control unit. By introducing a multi-converter collaborative control structure on the low-voltage side of the transformers, it achieves balanced power flow redistribution, unbalanced power flow management, and power quality control. This device can improve transformer capacity utilization, reduce operating losses, and achieve capacity mutual assistance among transformers based on load characteristics. It is suitable for flexible power flow regulation among multiple power transformers and for managing power quality issues such as high / low voltage and harmonics.

Description

Technical Field

[0001] This invention relates to the field of power system transformer power flow optimization technology, and in particular to a power flow controller between transformers. Background Technology

[0002] With the advancement of the construction of new power systems, the load structure and operation mode of power systems have undergone significant changes. On the one hand, the large-scale connection of residential loads, commercial loads, and electrical equipment such as distributed renewable energy and electric vehicle charging facilities has resulted in transformer loads exhibiting characteristics such as strong time-varying nature, uneven phase distribution, and frequent power fluctuations. On the other hand, constrained by historical planning and construction conditions, existing power systems generally adopt an operation mode of independent power supply by a single transformer, and the connection methods used between transformers have weak power flow distribution capabilities, making it difficult to achieve flexible power flow allocation.

[0003] Against this backdrop, various problems have gradually emerged during the operation of distribution substations. For example, some distribution transformers experience localized forward and reverse overloads during peak hours, while adjacent substations still have excess capacity. The overlap of peak electricity consumption from agricultural production and tourism has led to severe three-phase load imbalances on the low-voltage side of some substations, resulting in excessive neutral current, increased line losses, and even voltage exceeding limits. Simultaneously, the widespread use of nonlinear loads has increased harmonic content and degraded power quality on the low-voltage side of substations. These problems not only affect power supply reliability and power quality but also accelerate the aging of distribution transformers and line equipment, increasing operation and maintenance costs.

[0004] To address the issues of insufficient capacity or deteriorating operational quality of distribution transformers, existing technologies typically employ the following methods for modification or mitigation: The first method is to replace / increase the capacity of the transformer: This method involves high investment, long cycle, and more than 30% of the capacity cannot be fully utilized due to load imbalance. In addition, it is easy to cause low equipment utilization and large no-load loss for fluctuating loads, resulting in poor economic efficiency.

[0005] The second approach is to install localized management devices (such as adding transformer area energy storage, reactive power compensation, active filtering, etc.): These devices usually have a single function. Although they can improve specific power quality indicators, they are inefficient, have limited capacity and voltage regulation capabilities, and the single-phase problem remains unresolved. They cannot achieve flexible power flow distribution and load balancing between transformers, making it difficult to fundamentally optimize system operation.

[0006] The third approach is to use flexible interconnection devices: these devices focus on active power transmission between distribution stations, but their control strategies are complex, the problem of single-phase heavy overload has not been solved, the voltage regulation capability is weak, and it is difficult to achieve multiple power quality optimization goals such as three-phase imbalance management and harmonic suppression while simultaneously achieving power flow regulation.

[0007] In summary, existing technologies lack a method for flexibly allocating the surplus capacity and power quality of multiple transformers, thereby achieving integrated power flow control and comprehensive power quality management. Summary of the Invention

[0008] The main objective of this invention is to provide a power flow controller between transformers, which can solve the problem of the lack of a method in the prior art that can flexibly allocate the spare capacity and power quality of multiple transformers, and realize the integrated function of power flow regulation and comprehensive power quality management.

[0009] To achieve the above objectives, the first aspect of the present invention provides a power flow controller between transformers, the power flow controller comprising: a first port, a first transformer, a second transformer, a first converter, a second converter, a coupling module, a third converter, a second port, a DC bus, and a comprehensive control unit; The first port is used to connect to the power grid line or electrical load; The primary side of the first transformer is connected to the first port, and the secondary side of the first transformer is connected to the output input terminal of the coupling module. The primary side of the second transformer is connected to the first port, and the secondary side of the second transformer is connected to the AC side of the first converter; the DC side of the first converter is connected to the DC bus. The DC side of the second converter is connected to the DC bus, and the AC side of the second converter is connected to the input side of the coupling module; The output terminal of the coupling module is connected to the second port, and the coupling module is used for electrical coupling between the first transformer, the second converter, and the second port. The DC side of the third converter is connected to both ends of the DC bus, and the AC side of the third converter is flexibly connected to the electrical path between the output terminal of the first transformer and the second port. The second port is used to connect to the power grid line or electrical load; The integrated control unit is connected to the first converter, the second converter, and the third converter. It is used to collect electrical parameters and generate drive signals for the first converter, the second converter, and the third converter according to the control method, so as to coordinate the operation of the converters and realize power flow regulation between the first transformer and the second transformer.

[0010] In one feasible implementation, the power flow controller further includes a support capacitor, the two ends of which are respectively connected to the two ends of the DC bus, and the midpoint of the support capacitor is grounded.

[0011] In one feasible implementation, the AC side of the third converter is connected to the second port.

[0012] In one feasible implementation, the AC side of the third converter is connected to the output terminal of the first transformer and the output input terminal of the coupling module.

[0013] In one feasible implementation, the coupling module includes: a first coupling transformer, a second coupling transformer, a third coupling transformer, an input-side interface, an output-side input terminal, and an output-side output terminal; The input sides of the first coupling transformer, the second coupling transformer, and the third coupling transformer adopt a Y-type connection, an yn-type connection, or a d-type connection according to a three-phase three-wire system or a three-phase four-wire system. The same-named terminals on the other side of the first, second, and third coupling transformers serve as the input terminals of the output side of the coupling module, while the non-same-named terminals serve as the output terminals.

[0014] In one feasible implementation, for the first converter, the integrated control unit is used to collect the DC-side capacitor voltage of the power flow controller and input a given reactive power reference value, and generate a first drive signal for the first converter by using reactive power compensation and voltage regulation control to realize the reactive power compensation function and the voltage stabilization of the DC side of the power flow controller.

[0015] In one feasible implementation, for the second converter, the integrated control unit is used to collect the output voltage of the second transformer and the output voltage of the coupling module, and uses voltage regulation control to generate a second drive signal for the second converter, thereby regulating the voltage of the second port bus and reducing the self-loss of the power flow controller.

[0016] In one feasible implementation, for the third converter, the integrated control module is used to collect the load current and the output current of the first transformer, and, in combination with the given power flow regulation coefficient, generate the third drive signal of the third converter using power quality management and power flow control, so as to realize power flow regulation, asymmetry management and harmonic management between the first transformer and the second transformer.

[0017] In one feasible implementation, when the second port bus adopts a three-phase three-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase three-phase system or a three-phase four-wire system; when the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase four-wire system, the neutral line can be grounded or left floating.

[0018] In one feasible implementation, when the second port bus adopts a three-phase four-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase four-wire system.

[0019] The embodiments of the present invention have the following beneficial effects: This invention provides a power flow controller between transformers, comprising: a first port, a first transformer, a second transformer, a first converter, a second converter, a coupling module, a third converter, a second port, a DC bus, and a comprehensive control unit; the first port is used to connect to a power grid line or an electrical load; the primary side of the first transformer is connected to the first port, and the secondary side of the first transformer is connected to the output input terminal of the coupling module; the primary side of the second transformer is connected to the first port, and the secondary side of the second transformer is connected to the AC side of the first converter; the DC side of the first converter is connected to the DC bus; the DC side of the second converter is connected to the DC bus, and the AC side of the second converter is connected to... The coupling module is connected to the input side of the coupling module; the output terminal of the coupling module is connected to the second port, and the coupling module is used for electrical coupling between the first transformer, the second converter, and the second port; the DC side of the third converter is connected to both ends of the DC bus, and the AC side of the third converter is flexibly connected to the electrical path between the output terminal of the first transformer and the second port; the second port is used to connect to the power grid line or electrical load; the integrated control unit is connected to the first converter, the second converter, and the third converter, and is used to collect electrical parameters and generate drive signals for the first converter, the second converter, and the third converter according to the control method, so as to coordinate the operation of the converters and realize power flow regulation between the first transformer and the second transformer.

[0020] This application achieves flexible and precise control of power flow between transformers through a clever combination of dual transformers, multiple converters, and coupling modules, along with the coordinated control of a comprehensive control unit. It can dynamically adjust the converter output based on real-time electrical parameters, significantly improving the accuracy and response speed of power flow control between transformers. Furthermore, the multiple converters simultaneously achieve comprehensive power quality management, addressing multiple power quality optimization objectives such as high / low voltage and harmonics. This effectively overcomes the lack of flexibility in traditional methods, optimizes grid power distribution, enhances system stability and reliability, adapts to diverse operating conditions, and ensures the continuous and stable operation of electrical equipment. It has high practical and promotional value in the field of power transmission. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] in: Figure 1 This is one of the topology diagrams of a transformer power flow controller (TPFC) in an embodiment of the present invention; Figure 2 This is a second schematic diagram of a transformer power flow controller (TPFC) topology in an embodiment of the present invention; Figure 3 This is a schematic diagram of the coupling module topology of a transformer power flow controller (TPFC) in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the control principle of an inter-transformer power flow controller according to an embodiment of the present invention; Figure 5 This is a diagram illustrating the DC bus voltage control effect of a power flow controller between transformers in an embodiment of the present invention. Figure 6 This is one of the power quality management effect diagrams of an inter-transformer power flow controller in an embodiment of the present invention; Figure 7 This is the second illustration of the power quality management effect of an inter-transformer power flow controller in an embodiment of the present invention; Figure 8 This is a diagram illustrating the voltage regulation effect of a power flow controller between transformers in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1 , Figure 1 This is one of the topology diagrams of a transformer power flow controller (TPFC) according to an embodiment of the present invention, such as... Figure 1 The power flow controller (TPFC) between transformers shown includes: a first port 1, a first transformer 2, a second transformer 3, a first converter 4, a supporting capacitor 5, a second converter 6, a coupling module 7, a third converter 8, a second port 9, a DC bus 10, and a comprehensive control unit 11. The first port serves as a high-voltage busbar, used to connect to power grid lines or electrical loads; The primary side of the first transformer is connected to the first port, and the secondary side of the first transformer is connected to the output input terminal of the coupling module. The primary side of the second transformer is connected to the first port, and the secondary side of the second transformer is connected to the AC side of the first converter. The DC side of the first converter is connected to the DC bus; the first converter is used to realize bidirectional AC / DC conversion, stabilize the DC voltage of the DC bus 10, and compensate the reactive power of the power grid system. The two ends of the supporting capacitor 5 are respectively connected to the two ends of the DC bus 10, and the midpoint is grounded to provide a neutral point and stabilize the voltage of the DC bus 10. The DC side of the second converter is connected to the DC bus, and the AC side of the second converter is connected to the input side of the coupling module; this is used to realize voltage control and harmonic compensation functions. The output terminal of the coupling module is connected to the second port, and the coupling module is used for electrical coupling between the first transformer, the second converter, and the second port. The DC side of the third converter is connected to both ends of the DC bus, and the AC side of the third converter is flexibly connected to the electrical path between the output terminal of the first transformer and the second port. The third converter is used for imbalance control and harmonic compensation of the output current of the first transformer 2, and to realize power flow distribution between the first transformer 2 and the second transformer 3. For example, Figure 1 The AC side of the third converter shown is connected to the second port; see also [reference needed]. Figure 2 , Figure 2 This is a second schematic diagram of a transformer power flow controller (TPFC) topology in an embodiment of the present invention, as shown below. Figure 2 The AC side of the third converter shown is connected to the output terminal of the first transformer (i.e., the secondary side of the first transformer) and the output input terminal of the coupling module.

[0025] The second port is used to connect to the power grid line or electrical load, and can provide a power interface for the load; such as Figure 1 The second port 9 connects to the output terminal of the coupling module 7 and the AC power load of the third converter 8, providing a power interface for the load. The integrated control unit is connected to the first converter, the second converter, and the third converter. It is used to collect electrical parameters and generate drive signals for the first converter, the second converter, and the third converter according to the control method, so as to coordinate the operation of the converters and realize power flow regulation between the first transformer and the second transformer.

[0026] This invention provides a power flow controller for inter-transformer systems. Through a clever combination of two ports, dual transformers, multiple converters, and coupling modules, along with coordinated control of a comprehensive control unit, it achieves flexible and precise power flow control between transformers. It can dynamically adjust converter output based on real-time electrical parameters, significantly improving the accuracy and response speed of power flow control between transformers. Furthermore, by using multiple converters, it can simultaneously achieve comprehensive power quality management, including three-phase imbalance mitigation and harmonic suppression, thus achieving multiple power quality optimization goals. It effectively overcomes the lack of flexibility in traditional methods, optimizes grid power distribution, enhances system stability and reliability, adapts to diverse operating conditions, and ensures the continuous and stable operation of electrical equipment. It has high practical and promotional value in the field of power transmission.

[0027] In one feasible implementation, see [reference needed]. Figure 3 , Figure 3 This is a schematic diagram of the coupling module topology of a transformer power flow controller (TPFC) according to an embodiment of the present invention, as shown below. Figure 3 The coupling module shown includes: a first coupling transformer 71, a second coupling transformer 72, a third coupling transformer 73, an input side interface 74, an output side input terminal 75, and an output side output terminal 76; The input sides of the first, second, and third coupling transformers are connected in a Y-type, yn-type, or d-type configuration according to a three-phase three-wire or three-phase four-wire system. The same-named terminals on the other side of the first, second, and third coupling transformers serve as the input terminals of the output side of the coupling module, and the non-same-named terminals serve as the output terminals.

[0028] In one feasible implementation, when the second port bus adopts a three-phase three-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase three-phase system or a three-phase four-wire system; when the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase four-wire system, the neutral line can be grounded or left floating; when the second port bus adopts a three-phase four-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase four-wire system.

[0029] This application introduces a power flow regulation structure (i.e., the aforementioned power flow controller) consisting of a converter and coupling module on the low-voltage side of the transformer, achieving flexible distribution of transformer output power and improving the overall capacity utilization of the distribution substation. It significantly improves the three-phase imbalance problem in the distribution substation, reduces losses, extends transformer lifespan, and enhances system operational safety. It also maintains the second-port bus voltage within a reasonable range, ensuring the normal and safe operation of user equipment. In summary, this inter-transformer power flow controller (TPFC) is particularly suitable for widespread application in distribution substations of different sizes and load characteristics.

[0030] In one feasible implementation, for the first converter, the integrated control unit is used to acquire the DC-side capacitor voltage (i.e., DC bus voltage) of the power flow controller. U dc ) and input the given reactive power reference value Q abc The first drive signal for the first converter is generated using reactive power compensation and voltage stabilization control to achieve reactive power compensation and voltage stabilization on the DC side of the power flow controller. For example, the control objective of the control method for the first converter is to stabilize the DC voltage of the DC bus 10 while compensating for reactive power in the power grid system. The control process can be as follows: the integrated control unit monitors the DC bus voltage in real time. U dc Compare it with a reference value (e.g., 800V, see...) Figure 5 The switching state of the first converter is adjusted through feedback control (such as PID regulation) to keep the DC voltage stable. Simultaneously, based on the reactive power reference value... Q abc * Controls the injection or absorption of reactive power by the first converter to improve the power factor. This ensures rapid stabilization of the DC-side voltage of the TPFC (transition process approximately 0.3s, see...). Figure 5 It also supports the effect of system reactive power demand.

[0031] The output of the first converter U dc and Q abc * Satisfies the following expression:

[0032]

[0033] In the formula, U 1ab This is the line voltage on the AC side of the first converter; This is a power factor reference value, generally ; P The active power of the system; The bus voltage at the output terminal of the coupling module; This is the current on the second port side.

[0034] In one feasible implementation, for the second converter, the integrated control unit is used to acquire the output voltage of the second transformer. and the bus voltage at the output terminal of the coupling module A second drive signal for the second converter is generated using voltage regulation control to adjust the voltage of the second port bus and reduce the self-loss of the power flow controller. For example, the control objective of the control method for the second converter is to adjust the voltage of the second port 9 to a reasonable range (e.g., 330V, see...). Figure 8 ), and reduce the TPFC's own losses. The control process can be as follows: The integrated control unit compares the difference between the output voltage of the second transformer and the bus voltage at the output terminal of the coupling module ( The output of the second converter is adjusted through voltage control strategies (such as feedforward or feedback control); the second converter acts as a voltage source, injecting compensation voltage to offset the effects of line voltage drop or load fluctuations, thereby maintaining load-side voltage stability, preventing voltage overshoot, and improving power supply quality. Figure 8 The voltage regulation effect was demonstrated, showing that the load-side voltage was increased from 280V to 330V.

[0035] The voltage output of the second converter control coupling module Satisfy the following expression:

[0036] or

[0037] In the formula, This is the output voltage of the first transformer; This is the output voltage of the second transformer; This is the reference value for the bus voltage at the output terminal of the coupling module.

[0038] In one feasible implementation, for the third converter, the integrated control module is used to collect the current on the second port side. With the output current of the first transformer Combined with the given power flow control coefficient kThe third driving signal for the third converter is generated using power quality management and power flow control to achieve power flow regulation, asymmetry control, and harmonic control between the first transformer and the second transformer. For example, the control objective of the control method for the third converter is to achieve power flow distribution between the first transformer 2 and the second transformer 3, while simultaneously controlling three-phase imbalance and harmonics. The control process can be as follows: the integrated control unit determines the power flow based on the power flow regulation coefficient... k (like k =1 or k =2, see Figure 6 and Figure 7 Distribute transformer load. For example, k When =1, the power flow is uniformly distributed. I F1 =22.5A, I F2 =22.5A), k When the power flow is equal to 2, it is distributed proportionally. I F1 =15A, I F2 =30A); simultaneously, by detecting the current imbalance and harmonic content, the third converter injects compensation current to balance the three-phase load and filter out harmonics. This significantly reduces the current imbalance (from 65% to below 2%), enabling flexible power flow control and improved power quality. Figure 6 and Figure 7 Showing different k The effect of controlling the value.

[0039] The output of the third converter S 2 satisfies the following expression:

[0040]

[0041]

[0042] In the formula, k This refers to the tidal flow control coefficient. S L This represents the total power at the second port. S 1 represents the output power of the first transformer; S 2 represents the output power of the second transformer; This is the positive-sequence component of the output current of the third converter; This represents the positive-sequence component of the current at the second port. This represents the positive-sequence component of the output current of the first transformer.

[0043] Figure 4This is a schematic diagram illustrating the control principle of an inter-transformer power flow controller according to an embodiment of the present invention. See also... Figure 4 The integrated control module collects the DC-side capacitor voltage of the TPFC (i.e., the DC bus voltage). U dc ) and input the given reactive power reference value Q abc The system employs reactive power compensation and voltage regulation control to generate the drive signal for the first converter, achieving reactive power compensation and voltage stabilization on the DC side of the TPFC. The integrated control module acquires the output voltage of the second transformer. and coupling module output side outgoing bus voltage A voltage regulation control is used to generate the drive signal for the second converter, thereby regulating the voltage at the second port and reducing the losses of the TPFC itself; the integrated control module collects the current at the second port. With the output current of the first transformer Combined with the given power flow control coefficient k The third converter is driven by power quality management and power flow control, which realizes power flow regulation, asymmetry management, and harmonic management between the first and second transformers.

[0044] See Figure 5 The diagram shows the DC bus voltage control effect of a power flow controller between transformers. U dc The DC bus voltage is controlled by the first converter after power-on. After a transition period of about 0.3 seconds, the DC bus voltage reaches a stable state with a value of about 800V. U dc1 , U dc2 The voltages of the upper and lower arms of the supporting capacitor are approximately equal, fluctuating within a small range, and both remain stable at around 400V.

[0045] Figure 6 This is one of the power quality management effect diagrams of an inter-transformer power flow controller in an embodiment of the present invention; Figure 7 This is the second power quality management effect diagram of a power flow controller between transformers in an embodiment of the present invention. See also... Figure 6 , Figure 7 The control effect at different power flow control coefficients. Figure 6 Mid-current regulation coefficient k =1, Figure 7 Mid-current regulation coefficient k =2.

[0046] in I L This is the load current, which is also the output current of the low-voltage side of the first transformer without control. Figure 6 , Figure 7 In the middle, the load is exactly the same, therefore I F They are exactly the same, with a current imbalance of 65%; I F1 For the output current of the first transformer load side, I F2 This is the output current on the load side of the second transformer. Figure 6 , Figure 7 In the middle, after being controlled, I F1 , I F2 The unbalance of all three phases is less than 2%, which shows that the third converter effectively balances the three-phase current of the first and second transformers. Figure 6 middle I F1 For 22.5A, I F2 It is 22.5A. Figure 7 middle I F1 For 15A, I F2 The value is 30A. It can be seen that by giving a power flow control coefficient, the power flow between the first and second transformers can be rationally distributed, thus achieving power flow control between transformers.

[0047] See Figure 8 This demonstrates the voltage regulation effect of a power flow controller between transformers, in which... U F1 This is the low-voltage side voltage of the first transformer, with an effective value of 280V for each phase. U F2 This is the load-side voltage, with an effective value of 330V for each phase.

[0048] This invention discloses a Transformer Power Flow Controller (TPFC) for power flow regulation and power quality management among multiple power transformers. The controller includes two ports, a first transformer, a second transformer, three controllable converters, a DC bus, a coupling module, and a comprehensive control unit. By introducing a multi-converter collaborative control structure on the low-voltage side of the transformers, it achieves balanced power flow redistribution, unbalanced power flow management, and power quality control. This device can improve transformer capacity utilization, reduce operating losses, and achieve capacity mutual assistance among transformers based on load characteristics. It is suitable for flexible power flow regulation among multiple power transformers and for managing power quality issues such as high / low voltage and harmonics.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A power flow controller between transformers, characterized in that, The power flow controller includes: a first port, a first transformer, a second transformer, a first converter, a second converter, a coupling module, a third converter, a second port, a DC bus, and a comprehensive control unit; The first port is used to connect to the power grid line or electrical load; The primary side of the first transformer is connected to the first port, and the secondary side of the first transformer is connected to the output input terminal of the coupling module. The primary side of the second transformer is connected to the first port, and the secondary side of the second transformer is connected to the AC side of the first converter; the DC side of the first converter is connected to the DC bus. The DC side of the second converter is connected to the DC bus, and the AC side of the second converter is connected to the input side of the coupling module; The output terminal of the coupling module is connected to the second port, and the coupling module is used for electrical coupling between the first transformer, the second converter, and the second port. The DC side of the third converter is connected to both ends of the DC bus, and the AC side of the third converter is flexibly connected to the electrical path between the output terminal of the first transformer and the second port. The second port is used to connect to the power grid line or electrical load; The integrated control unit is connected to the first converter, the second converter, and the third converter. It is used to collect electrical parameters and generate drive signals for the first converter, the second converter, and the third converter according to the control method, so as to coordinate the operation of the converters and realize power flow regulation between the first transformer and the second transformer.

2. The power flow controller according to claim 1, characterized in that, The power flow controller also includes a support capacitor, the two ends of which are respectively connected to the two ends of the DC bus, and the midpoint of the support capacitor is grounded.

3. The power flow controller according to claim 1, characterized in that, The AC side of the third converter is connected to the second port.

4. The power flow controller according to claim 1, characterized in that, The AC side of the third converter is connected to the output terminal of the first transformer and the output input terminal of the coupling module.

5. The power flow controller according to claim 1, characterized in that, The coupling module includes: a first coupling transformer, a second coupling transformer, a third coupling transformer, an input side interface, an output side input terminal, and an output side output terminal; The input sides of the first coupling transformer, the second coupling transformer, and the third coupling transformer adopt a Y-type connection, an yn-type connection, or a d-type connection according to a three-phase three-wire system or a three-phase four-wire system. The same-named terminals on the other side of the first, second, and third coupling transformers serve as the input terminals of the output side of the coupling module, while the non-same-named terminals serve as the output terminals.

6. The power flow controller according to claim 1, characterized in that, For the first converter, the integrated control unit is used to collect the DC-side capacitor voltage of the power flow controller and the input given reactive power reference value, and to generate the first drive signal of the first converter by using reactive power compensation and voltage regulation control, so as to realize the reactive power compensation function and the voltage stabilization of the DC side of the power flow controller.

7. The power flow controller according to claim 1, characterized in that, For the second converter, the integrated control unit is used to collect the output voltage of the second transformer and the bus voltage at the output terminal of the coupling module, and uses voltage regulation control to generate the second drive signal of the second converter, thereby realizing the regulation of the second port bus voltage and reducing the self-loss of the power flow controller.

8. The power flow controller according to claim 1, characterized in that, For the third converter, the integrated control module is used to collect the load current and the output current of the first transformer, and combine them with the given power flow regulation coefficient to generate the third drive signal of the third converter using power quality management and power flow control, so as to realize power flow regulation, asymmetry management and harmonic management between the first transformer and the second transformer.

9. The power flow controller according to claim 1, characterized in that, When the second port bus adopts a three-phase three-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase three-phase system or a three-phase four-wire system; when the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the output side input terminal of the coupling module, and the output side output terminal of the coupling module adopt a three-phase four-wire system, the neutral line can be grounded or left floating.

10. The power flow controller according to claim 1, characterized in that, When the second port bus adopts a three-phase four-wire system, the AC side of the second converter, the AC side of the third converter, the input side of the coupling module, the input terminal of the output side of the coupling module, and the output terminal of the coupling module adopt a three-phase four-wire system.

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