Unified power flow controller and method of controlling the same

Abstract

This invention relates to the field of power distribution network technology and discloses a unified power flow controller and its control method. This unified power flow controller reduces the requirements of the unified power flow controller on external power sources in terms of voltage and power flow regulation by connecting back-to-back converter modules to energy storage modules. It can provide rapid voltage and frequency support to the second power grid under external disturbances and related renewable energy fluctuations. Furthermore, by designing a switching module in the series feeder unit, the switching module can switch from series branch mode to bypass branch mode when the unified power flow controller is in a fault state. This quickly isolates the faulty unified power flow controller from the series feeder, enabling bypass connection between the first and second power grids. Thus, while effectively isolating the faulty controller, it ensures uninterrupted power supply to the second power grid, meeting the high reliability operation requirements of high-voltage distribution networks.

Description

Technical Field

[0001] This invention relates to the field of power distribution network technology, and in particular to a unified power flow controller and its control method. Background Technology

[0002] As the energy transition continues to deepen and a new power system based on new energy sources is being built at an accelerated pace, the high-voltage distribution network, as the core hub connecting the transmission network and end users, directly affects energy supply security and user electricity experience with its power supply reliability and fault response capabilities. The large-scale integration of distributed new energy sources has further exacerbated the fluctuations in the operation of the distribution network, placing more stringent requirements on the rapid handling and continuous power supply capabilities under fault conditions of the distribution network.

[0003] The traditional unified power flow controller (UPFC), as a mature power grid flexible control device, has been widely used in high-voltage transmission network scenarios. Its design logic is highly compatible with the N-1 redundancy planning configuration of the transmission network. It can achieve power flow control by relying on multi-path power supply layout, and can ensure the continuity of regional power supply by relying on redundancy support when core equipment fails, effectively maintaining the safe and stable operation of the transmission network.

[0004] However, high-voltage distribution networks are constrained by planning principles, construction costs, and user load distribution, and do not adopt the redundant configuration of transmission networks. The power supply path is relatively simple. Traditional unified power flow controllers are designed based on the operating characteristics of transmission networks and do not fully consider the non-redundant planning characteristics of high-voltage distribution networks. When applied directly, they lack adaptability. That is, once the core series components fail, it will directly cause the corresponding line to lose voltage. Moreover, there is a lack of effective fault isolation and rapid power supply restoration mechanisms. At this time, the impact of voltage loss will be quickly transmitted to the user-side load, resulting in power outage. This not only fails to meet the high reliability operation requirements of high-voltage distribution networks, but also restricts the large-scale promotion of efficient power flow control technology in distribution network scenarios, making it difficult to adapt to the development requirements of high-voltage distribution networks under new power systems. Summary of the Invention

[0005] In view of this, the present invention provides a unified power flow controller and its control method, which solves the technical problem that once the core series component of the traditional unified power flow controller fails, it will directly cause the corresponding line to lose voltage, and lacks an effective fault isolation and fast power supply restoration mechanism.

[0006] The first aspect of the present invention provides a unified power flow controller, which is installed between a first power grid and a second power grid, and includes: a back-to-back converter module, an energy storage device module, a parallel feeder unit and a series feeder unit;

[0007] The energy storage device module is electrically connected to the DC side of the back-to-back converter module; the energy storage device module is used to provide frequency and voltage support to the second power grid through the back-to-back converter module.

[0008] The back-to-back converter module is electrically connected to the transformer station bus of the first power grid through the parallel feeder unit;

[0009] The series feeder unit includes a series transformer and a switch module; the back-to-back converter module is electrically connected to the series transformer, the series transformer is electrically connected to the switch module, and the first power grid is electrically connected to the access point of the second power grid through the switch module;

[0010] The switching module is used to switch from series branch mode to bypass branch mode in response to the fault state of the unified power flow controller; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid, and the bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0011] In one embodiment, the back-to-back converter module includes a series-side converter and a parallel-side converter, which are connected in parallel. Both the series-side converter and the parallel-side converter are connected to the same DC bus, and the DC bus is electrically coupled to the energy storage device module through a chopper.

[0012] In one embodiment, the parallel feeder unit includes a parallel transformer, one end of which is electrically connected to the parallel side of the back-to-back converter module, and the other end of which is electrically connected to the substation bus of the first power grid.

[0013] In one embodiment, the switch module includes a first switch, a second switch, and a bypass switch, wherein the first power grid is connected in series with the second power grid through the first switch and the second switch to form the series feeder;

[0014] One end of the bypass switch is connected to the substation side of the first switch, and the other end of the bypass switch is connected to the load side of the second switch.

[0015] The series transformer is connected between the first switch and the second switch.

[0016] In one embodiment, the switch module further includes a third switch and a TBS switch, the back-to-back converter module is electrically connected to the third switch, the third switch is bypassed to the TBS switch, and the TBS switch is electrically connected to the series transformer.

[0017] In one embodiment, the energy storage device module is provided with a power expansion interface for electrical connection to an external power source of the unified power flow controller.

[0018] In one embodiment, the unified power flow controller further includes: a relay protection device; the relay protection device is electrically connected to the series transformer and the switching module respectively;

[0019] The series transformer is used to detect the first current differential signal at both ends of the series transformer in real time. When the first current differential signal is abnormal, a first fault switching command is generated and sent to the relay protection device.

[0020] After the first fault switching command is configured on the relay protection device, it controls the tripping of the first switch, the second switch and the third switch, and closes the bypass switch when the second power grid meets the power supply conditions, thus forming the bypass branch mode.

[0021] In one embodiment, the unified power flow controller further includes: a fiber optic differential protection device; the fiber optic differential protection device is installed between the load side of the second switch and the second power grid; the relay protection device is electrically connected to the fiber optic differential protection device;

[0022] The fiber optic differential protection device is used to detect the second current differential signal of the series feeder in real time, and when the second current differential signal is abnormal, it generates a second fault switching command and sends it to the relay protection device.

[0023] After the second fault switching command is configured on the relay protection device, the TBS switch is closed, the second switch, the substation-side internal switch and the first switch are tripped, the substation-side internal switch is reclosed after a delay, and after the substation-side internal switch is reclosed, and the bypass switch is closed under the condition that the second power grid meets the power supply requirements, thus forming the bypass branch mode.

[0024] In one embodiment, the unified power flow controller further includes: an optical fiber communication detection module; the optical fiber communication detection module is used to close the TBS switch through the relay protection device when a fault is detected in the unified power flow controller, and to detect the status of the optical fiber communication link between the first switch, the second switch and the substation-side in-station switch in real time.

[0025] The unified power flow controller is used to generate a third fault switching command and send it to the relay protection device based on the fault status of the unified power flow controller and the status of the optical fiber communication link when the optical fiber communication link is in normal communication status.

[0026] The third fault switching command is configured after the relay protection device, which controls the substation-side internal switch, the first switch and the second switch to exchange fault electrical quantity information in sequence, determine the fault range, and perform the opening operation of the first switch and the second switch according to the fault range, and perform the closing operation of the bypass switch to form the bypass branch mode.

[0027] In a second aspect, the present invention also provides a control method applied to the unified power flow controller described in the first aspect, the method comprising:

[0028] Detect the operating status of the unified power flow controller;

[0029] When the unified power flow controller is in normal operating state, it controls the switch module to execute the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid;

[0030] When the unified power flow controller is in a fault state, the switching module is controlled to switch from the series branch mode to the bypass branch mode; wherein, the bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0031] As can be seen from the above technical solutions, this invention reduces the requirements of the unified power flow controller on external power supply in terms of voltage and power flow regulation by connecting the back-to-back converter module to the energy storage device module. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuation scenarios. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from the series branch mode to the bypass branch mode when the unified power flow controller is in a fault state. This allows the unified power flow controller in a fault state to be quickly isolated from the series feeder and the first grid to be bypassed to the second grid. Thus, while effectively isolating the faulty controller, it ensures that the power supply to the second grid is not interrupted, realizes fault self-healing and zero-sensory power supply switching, and avoids the problem that the failure of the unified power flow controller will directly cause the corresponding line to lose voltage. It can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios. Attached Figure Description

[0032] 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.

[0033] Figure 1 A schematic diagram of a unified power flow controller provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the extended structure of the energy storage device module provided in an embodiment of the present invention;

[0035] Figure 3 Another structural schematic diagram of the unified power flow controller provided in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of the switch module provided in an embodiment of the present invention;

[0037] Figure 5 This is another structural schematic diagram of the switching module provided in an embodiment of the present invention;

[0038] Figure 6 A flowchart illustrating a control method for a unified power flow controller provided in an embodiment of the present invention;

[0039] Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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.

[0041] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a replaceable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0043] With the explosive growth of new energy sources, the large-scale integration of new loads such as power electronics and other new energy sources poses a significant challenge to the safe operation of the power grid. Because wind and solar resources are significantly constrained by natural weather conditions, their output exhibits strong randomness and anti-peak-shaving characteristics (e.g., high solar power generation at midday with low load, followed by peak demand in the evening when solar power is depleted). This results in significant fluctuations in daily net load, a sharp increase in peak-to-valley differences, and a marked increase in short-term load ramp-up rates. Accidental factors such as weather changes can cause sudden changes in new energy output or lead to transient power imbalances in local power grids, affecting the operational stability of generating units, especially small units. Disturbances caused by external faults, such as voltage dips, can affect the grid connection of voltage-sensitive equipment (e.g., solar power equipment), and in severe cases, can lead to other problems, further impacting the safe operation of the power grid.

[0044] For high-voltage distribution networks of 1kV-20kV, the integration of new energy sources is generally in the form of distributed photovoltaics. Furthermore, due to various reasons, energy storage facilities may not be included, resulting in poor regulation capabilities and placing greater pressure on the power balance and absorption of the distribution network. In addition, the distribution network is closely related to user activities, and the total number of distribution lines is far greater than that of transmission lines. Because faults in distribution lines affect the voltage of other lines on the same bus, voltage-sensitive equipment on other lines, such as photovoltaic equipment, may further exacerbate voltage and frequency disturbances (especially with small generator sets on the lines).

[0045] A unified power flow controller is a device that connects two or more voltage source converters sharing a DC bus to a power transmission system in parallel and series configurations, and can simultaneously control line impedance, voltage amplitude, and phase angle.

[0046] Currently, the structural design and control logic of traditional unified power flow controllers (UPFCs) are primarily adapted to the operating characteristics of high-voltage transmission networks. Their series-connected transformers, as the core power transmission and conversion components, will directly cause voltage loss in the connected transmission lines if they fail. In high-voltage transmission network scenarios, high-voltage transmission lines are constructed according to the "N-1" planning and configuration principle, with sufficient redundancy in the network layout. The same power supply area is typically equipped with backup lines or double (or even multiple) lines. When any line fails, the load is still supplied by other lines, ensuring power continuity. The loads in the relevant power supply areas will not experience voltage loss, and power continuity can be effectively guaranteed. Therefore, existing UPFCs do not require additional fault emergency bypass structures to meet the reliability operation requirements of high-voltage transmission networks.

[0047] High-voltage distribution networks are constrained by multiple factors, including planning principles, construction costs, user load density, and geographical conditions, making it impossible to plan and configure them according to the "N-1" standard of high-voltage transmission networks. Their power supply paths are relatively simple, often with only a single power supply line in the same area, lacking sufficient backup line redundancy. The fault tolerance of the power grid itself is far lower than that of high-voltage transmission networks. Traditional UPFCs (Upgraded Power Distribution Systems) are not designed to adapt to this core operational characteristic of high-voltage distribution networks. For example, a fault in the series-side transformer will directly lead to voltage loss in the connected distribution network lines, severely impacting the operational reliability of the served devices. Therefore, existing UPFCs face bottlenecks in large-scale application in high-voltage distribution network scenarios and cannot meet the high reliability requirements of high-voltage distribution networks.

[0048] To address the high power quality requirements of power systems with renewable energy as the main component in high-voltage distribution networks, this application proposes a unified power flow controller. This controller uses a back-to-back converter connection method in the distribution network and incorporates energy storage modules to enhance power flow and voltage regulation. It provides voltage and frequency support services when service targets (such as loads and microgrids) are subjected to transient disturbances, and includes a bypass design to ensure the operational reliability of series-connected feeders.

[0049] like Figure 1As shown in the figure, this application embodiment provides a unified power flow controller 300, which is installed between a first power grid 200 and a second power grid 400. The first power grid 200 refers to a high-voltage transmission backbone network (220kV and above) covering a wide area, and includes substation buses and substation-side switches. The second power grid 400 refers to various power loads connected to the distribution network, including but not limited to industrial users, commercial users, residential users, and microgrids formed by distributed power aggregation. The unified power flow controller 300 is precisely embedded in the key power flow lines between the upper-level backbone network and the second power grid 400 through series-side feeders, realizing real-time closed-loop control of key power quality indicators such as power flow distribution, node voltage, and power factor, significantly improving the dynamic response capability and operational resilience of the distribution network in scenarios with a high proportion of new energy access.

[0050] The unified power flow controller 300 in this application can be applied to distribution networks with voltage levels of 1-20kV. The first power grid 200 can be a large power grid with a voltage level of 10kV or 20kV, and the second power grid 400 can be a microgrid or directly connected to users.

[0051] like Figure 1 As shown, the unified power flow controller 300 proposed in this application embodiment includes: a back-to-back converter module 301, an energy storage device module 302, a parallel feeder unit 303, and a series feeder unit 304.

[0052] The energy storage device module 302 is electrically connected to the DC side of the back-to-back converter module 301; the energy storage device module 302 is used to provide frequency and voltage support to the second power grid 400 through the back-to-back converter module 301.

[0053] The energy storage module 302 can be a high-performance energy storage device (group / system). The energy storage module 302 is electrically connected to the DC bus of the back-to-back converter module 301. Through the charging and discharging functions of the energy storage module 302, the bus power flow can be adjusted and the bus voltage controlled. Simultaneously, the back-to-back converter module 301 can quickly output power to the second grid 400, providing frequency and voltage support for the second grid 400. In particular, when the unified power flow controller is disturbed, the charging and discharging functions of the energy storage module 302 can adjust the line load, thereby regulating the user-end voltage and the frequency of user-end small generating units (microgrid units), smoothing voltage fluctuations, correcting frequency deviations, and solving the voltage regulation and (small generating unit) frequency support function requirements.

[0054] The performance of the energy storage device module 302 should meet the requirements of the scenario, such as action response time, charging and discharging time, charging and discharging power, and the charging and discharging power required to match the scenario. It should also address voltage regulation, (transient) voltage support, frequency support, etc. The design requirements can be achieved by using energy storage device modules with different technical paths.

[0055] For example, for transient disturbances, energy storage devices using magnetic energy storage technology can be combined with those using electrochemical or lithium-ion battery energy storage technologies. For instance, in uncertain scenarios where charging or discharging demands exist simultaneously, if the time it takes for the energy storage device to fully charge or deplete its charge does not meet the scenario requirements, the energy storage device should not be at full capacity or completely empty. It is recommended to set intermediate values ​​based on empirical data and the specific scenario. For instance, in scenarios requiring both response speed and power capacity, energy storage devices using rapid-response technologies (such as magnetic energy storage) can be combined with other large-scale energy storage technologies (such as pumped hydro storage). Furthermore, if frequency regulation for microgrid-connected generators needs to be configured, the energy storage capacity of the energy storage device should reach the design value, or specific settings should meet relevant requirements.

[0056] Energy storage module 302 should be able to expand its applications, such as... Figure 2 As shown, the energy storage device module 302 is equipped with a power expansion interface, which is used for electrical connection with the external power supply of the unified power flow controller 300.

[0057] External power sources can be either new energy sources or traditional power sources, which can improve the system's ability to adjust the power quality of distribution network lines or further enhance the power flow regulation effect.

[0058] In this application, by adding an access energy storage device module 302, the dependence of the unified power flow controller 300 on external power supply is reduced. In distribution network and microgrid application scenarios with uncertain power conditions, the daily voltage adjustment or transient voltage support function is more effective than the classic method of the unified power flow controller 300.

[0059] The back-to-back converter module 301 is electrically connected to the transformer station bus of the first power grid 200 through the parallel feeder unit 303.

[0060] Preferably, the parallel feeder unit 303 includes a parallel transformer, one end of which is electrically connected to the parallel side of the back-to-back converter module 301, and the other end of which is electrically connected to the substation bus of the first power grid 200.

[0061] The transformer busbar of the first power grid 200 is the transformer busbar of the substation of the first power grid 200. As a key node for power transmission, it is coupled to the parallel side of the back-to-back converter module 301 to achieve local reactive power compensation, flexible active power flow control, and dynamic support for bus voltage. This connection method ensures the safe access of parallel-side equipment and ensures that during series-side faults, the parallel feeder unit 303 continuously provides voltage / frequency support to the upstream busbar to address power flow issues. The power supply capacity of the line should match the output capacity of the equipment, and no overload should occur during the output process to maintain the local stability of the main power grid.

[0062] The series feeder unit 304 includes a series transformer 341 and a switch module 342; the back-to-back converter module 301 is electrically connected to the series transformer 341, the series transformer 341 is electrically connected to the switch module 342, and the first power grid 200 is electrically connected to the access point of the second power grid 400 through the switch module 342.

[0063] The switching module 342 is used to switch from series branch mode to bypass branch mode in response to the fault state of the unified power flow controller 300; wherein, the series branch mode is used to connect the unified power flow controller 300 in series to the series feeder between the first power grid 200 and the second power grid 400, and the bypass branch mode is used to isolate the unified power flow controller 300 in the fault state from the series feeder and bypass the first power grid 200 and the second power grid 400.

[0064] Understandably, the switching module 342 responds to the fault or normal state of the unified power flow controller 300, thereby automatically performing mode switching, and realizing series side voltage injection and power flow directional regulation in series branch mode and bypass branch mode, or ensuring power supply continuity and power quality stability in bypass branch mode.

[0065] Preferably, under normal operating conditions, the switch module 342 is in series branch mode, connecting the unified power flow controller 300 in series with the series feeder between the first power grid 200 and the second power grid 400, enabling the unified power flow controller 300 to participate in power flow regulation and voltage support. When a fault is detected in the unified power flow controller 300, the switch module 342 automatically switches to bypass branch mode, connecting the first power grid 200 and the second power grid 400 via a bypass, and isolating the faulty unified power flow controller 300 from the series feeder. This achieves fault isolation of the unified power flow controller 300 without affecting the continuous power supply to the second power grid 400, ensuring that the reliability of the distribution network operation is not affected.

[0066] It should be noted that, by connecting the back-to-back converter module to the energy storage device module, the requirements of the unified power flow controller on the external power supply are reduced in terms of voltage and power flow regulation functions. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuation scenarios. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from the series branch mode to the bypass branch mode when the unified power flow controller is in a fault state. This allows the unified power flow controller in a fault state to be quickly isolated from the series feeder and the first grid to be bypassed to the second grid. Thus, while effectively isolating the faulty controller, it ensures that the power supply to the second grid is not interrupted, realizes fault self-healing and zero-sensory power supply switching, and avoids the problem that the failure of the unified power flow controller will directly cause the corresponding line to lose voltage. It can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios.

[0067] The following is for reference. Figure 3 The unified power flow controller of this application will be illustrated with a more specific embodiment.

[0068] In the above, as Figure 1 Based on the structure of the unified power flow controller shown, the back-to-back converter module includes a series-side converter and a parallel-side converter. The series-side converter and the parallel-side converter are connected in parallel. Both the series-side converter and the parallel-side converter are connected to the same DC bus. The DC bus is electrically coupled to the energy storage device module through a chopper.

[0069] Among them, the chopper is used to ensure the DC bus voltage is stable during the charging and discharging of high-performance energy storage equipment, and the converter can function normally in a "back-to-back" configuration.

[0070] It should be noted that during the operation of the energy storage device module, if the module can maintain voltage stability during power output, or if the device has a relatively weak impact on the DC bus voltage, small enough to meet the established engineering standards and design requirements, then the chopper that may have been used in the original plan can actually be omitted or removed.

[0071] In configuring secondary equipment, the general setup principles for back-to-back converter systems should be followed, but the management requirements for distribution network applications should also be considered, including but not limited to:

[0072] (1) The protection configuration scheme of the converter adopts the design concept based on functional area division. By dividing the overall system into multiple independent protection areas, the precise monitoring and isolation protection of each key module can be achieved. This scheme not only improves the reliability of equipment operation, but also facilitates the location of fault points, effectively prevents local anomalies from spreading to the entire system, and ensures the safe and stable operation of the converter under complex operating conditions.

[0073] (2) When the unified power flow controller is connected to the external AC line, it mainly relies on differential protection as its core main protection measure. This protection method can quickly and accurately identify and isolate various faults on the line. At the same time, in order to improve the overall protection reliability, distance protection and zero-sequence protection are also configured as effective backup protection. In the event of failure or non-operation of the main protection, these backup protections can intervene in time, thereby ensuring that the system can still maintain stable operation under various abnormal conditions and minimize the scope and duration of fault impact.

[0074] (3) In the power system design process, the protection strategy of the converter needs to be closely integrated with multiple AC-side related protection systems for coordination and matching. Specifically, its protection scheme should not only consider the characteristics and operating requirements of the converter itself, but also systematically integrate multi-level protection measures such as series transformer protection, parallel transformer protection, line protection and bus differential protection on the AC side, so as to ensure that the entire system can achieve fast, accurate and reliable operation under various fault conditions. This comprehensive design strategy aims to improve the overall safety and stability of the system through reasonable cooperation and logical coordination among various protections, thereby effectively isolating faults and ensuring the continuous and stable operation of power equipment.

[0075] (4) In the event of a transient overvoltage fault in the electrical system, the overvoltage protection module configured on the series-side converter must be able to quickly, accurately, and reliably activate its preset protective action mechanism. The core design objective of this protection mechanism is to ensure that when the system detects that the voltage amplitude exceeds the preset safety threshold, it can promptly trigger the corresponding control or isolation program, thereby effectively preventing overvoltage from causing irreversible insulation breakdown, thermal overload, or performance degradation to the precision power electronic components (such as capacitors) inside the series-side converter, and ensuring the continuous, stable, and safe operation of the entire converter and even the upstream and downstream power equipment.

[0076] (5) In order to ensure the stable and efficient operation of the series transformer in conjunction with the entire power distribution network, a comprehensive technical strategy that precisely matches the reliability requirements of the power distribution network lines is adopted for the specific application scenarios of the series transformer. Specifically, based on the operating characteristics and fault protection level of the power distribution network system, a customized protection scheme is configured for the series transformer 341 to achieve rapid and accurate protection of the equipment itself and the associated lines.

[0077] In some embodiments, such as Figure 3 and Figure 4 As shown, the switch module includes a first switch A1, a second switch A2 and a bypass switch A3. The first power grid is connected in series with the second power grid through the first switch A1 and the second switch A2 to form a series feeder.

[0078] One end of the bypass switch A3 is connected to the substation side of the first switch A1, and the other end of the bypass switch A3 is connected to the load side of the second switch A2.

[0079] A series transformer is connected between the first switch A1 and the second switch A2.

[0080] In special cases such as scenario environment, equipment limitations, and implementation traversal requirements, there may be more than one bypass switch A3, but the bypass switches A3 should cooperate with each other (such as setting simultaneous operation) so as not to affect the operational reliability of the line where the series transformer is located.

[0081] Preferably, when the first switch A1 and the second switch A2 are closed, the bypass switch A3 is in the open position, forming a series branch mode. At this time, the series transformer is connected to the series feeder, and the unified power flow controller regulates the power flow normally. When the first switch A1 or the second switch A2 needs to be disconnected due to fault or maintenance, the bypass switch A3 automatically closes, forming a bypass branch mode to ensure continuous power supply to the load, and the series transformer is safely isolated. At this time, the system seamlessly switches to the bypass power supply state, the series transformer is taken out of operation but the load continuity is not interrupted, fully demonstrating the high reliability and intelligent fault tolerance capability of the unified power flow controller.

[0082] Among them, the operation logic of each switch strictly follows the timing interlocking mechanism to prevent asynchronous closing and circulating current risks, and ensure that the distribution network still meets the power supply safety criteria under N-1 fault.

[0083] like Figure 3 As shown, PW line is a dedicated high-voltage distribution line for the series unit to connect to the substation bus, realizing the electrical connection between the series unit and the power grid. PW line 2 is the feeder of the parallel unit, and its connection point is located on the load side bus of the series transformer, undertaking the functions of reactive power compensation and voltage support.

[0084] For example, when the unified power flow controller fails, by controlling the first switch A1 and the second switch A2 to open, the series transformer is directly isolated from the series feeder and the series converter respectively. Through the line protection action, the substation switch trips and recloses, and the first switch A1 equipped with automation function is set to be blocked from power failure and closed, thus completing the result of controlling the first switch A1 and the second switch A2 to open, and completing the isolation between the series side line and the series transformer.

[0085] When the power grid and unified power flow controller are under normal operating conditions, the back-to-back converter modules and energy storage modules work together to regulate power flow and voltage. When the series-connected lines are disturbed by external faults, they provide voltage and frequency support to the secondary power grid. When the controller fails, power supply is maintained by the bypass module after the fault is isolated, and system reliability is ensured by the bypass. The energy storage module, as an auxiliary energy guarantee, enhances the power flow and voltage regulation effect and plays a major role in providing voltage and frequency support during disturbances. Through the above working mechanism, the controller is more adapted to the operating characteristics of high-voltage distribution networks than the original mode, and better meets the high reliability requirements of high-voltage distribution networks.

[0086] It should be noted that the unified power flow controller can carry out power flow regulation and voltage regulation under normal grid operating conditions. When the second grid is subjected to transient disturbances, it can provide emergency voltage and frequency support. When the unified power flow controller fails, it can quickly isolate the controller and restore power supply to the series-connected lines.

[0087] High-voltage distribution networks are power networks whose rated voltage levels conform to the 1-20kV high-voltage standards for distribution networks. They are used for power transmission and distribution, and connect substations with microgrids / loads. Normal operating conditions refer to the operation of all components of the controller, substation busbars, and service objects according to the preset operating mode, without fault phenomena, and with normal electrical parameters.

[0088] Transient disturbances refer to the power quality parameters of the load being served when the components of the unified power flow controller, the substation bus, the series-connected lines, and the load portion of the service object are operating in the preset mode without any faults, but other equipment in the power grid malfunctions or changes in parameters. In this application, voltage and frequency are specifically referred to as transient disturbances.

[0089] Power flow regulation is a control process that uses adjustable voltage components from back-to-back converter modules to regulate the distribution of active and reactive power in distribution network lines, thereby optimizing network losses and voltage levels.

[0090] Voltage regulation is a control process that uses back-to-back converter modules connected in parallel to the substation bus or series lines to output adjustable active and reactive power, thereby stabilizing the bus voltage or the voltage of the service object.

[0091] Voltage and frequency support refers to the rapid output of active and reactive power to the service object through the series side when the load of the service object is affected by transient disturbances and the voltage and frequency are affected, so as to prevent the voltage and frequency from changing temporarily.

[0092] In some embodiments, such as Figure 5 As shown, the switch module also includes a third switch A4 and a TBS switch. The back-to-back converter module is electrically connected to the third switch A4, the third switch A4 is bypassed to the TBS switch, and the TBS switch is electrically connected to the series transformer.

[0093] The TBS (Transformer Bypass Switch) is a thyristor-based bypass switch specifically designed to safely isolate a series transformer from the system during faults or maintenance. Simultaneously, through the coordinated action of the third switch A4 and the TBS switch (e.g., the third switch A4 closing and the TBS switch opening), the back-to-back converter modules can be directly connected to the series feeder, maintaining uninterrupted power flow control. This design significantly improves equipment maintainability and system resilience. If the TBS switch closes, the series transformer can be isolated from the line.

[0094] In some embodiments, the unified power flow controller further includes a relay protection device; the relay protection device is electrically connected to the series transformer and the switching module respectively;

[0095] The series transformer is used to detect the first current differential signal at both ends of the series transformer in real time. When the first current differential signal is abnormal, a first fault switching command is generated and sent to the relay protection device.

[0096] After the first fault switching command is configured on the relay protection device, it controls the tripping of the first switch A1, the second switch A2 and the third switch A4, and closes the bypass switch to form a bypass branch mode when the second power grid meets the power supply conditions.

[0097] The series transformer itself can detect the first current differential signal at both ends of the series transformer. If the first current differential signal exceeds a certain threshold, it indicates that the current at both ends of the series transformer is abnormal. Therefore, a first fault switching command needs to be generated. After the first fault switching command is generated and sent to the relay protection device, the first switch A1, the second switch A2, and the third switch A4 are tripped to isolate the unified power flow controller from the fault. The power supply conditions of the bypass switch A3 are verified by electrical quantity characteristics, such as detecting whether the bypass switch A3 has voltage on the substation side and no voltage or current on the user side, to avoid the risk of asynchronous grid connection. If the bypass switch A3 has voltage on the substation side and no voltage or current on the user side, the second power grid meets the power supply conditions. The bypass switch A3 is closed to form a temporary bypass power supply path to ensure continuous power supply to the load.

[0098] In some embodiments, the unified power flow controller further includes: a fiber optic differential protection device; the fiber optic differential protection device is installed between the load side of the second switch A2 and the second power grid; and a relay protection device is electrically connected to the fiber optic differential protection device.

[0099] The fiber optic differential protection device is used to detect the second current differential signal of the series feeder in real time, and when the second current differential signal is abnormal, it generates a second fault switching command and sends it to the relay protection device.

[0100] After the second fault switching command is configured on the relay protection device, the TBS switch is closed, the second switch A2, the substation-side internal switch and the first switch A1 are tripped, the substation-side internal switch is reclosed after a delay, and after the substation-side internal switch is reclosed, and under the condition that the second power grid meets the power supply conditions, the bypass switch A3 is closed to form a bypass branch mode.

[0101] Among them, the fiber optic differential protection device synchronously collects the current at both ends of the line (substation end and load end) at the speed of light. It determines whether there is a fault in the line by detecting the differential current signal at both ends. If the differential current signal shows a significant deviation, it determines that there is a fault and generates a second fault switching command to send to the relay protection device.

[0102] After receiving the instruction, the relay protection device controls each switch in the switch module, quickly isolating the faulty section and preparing for the subsequent closing of the bypass switch A3 to restore power. In the event of a fault, the relay protection device first closes the TBS switch to isolate the series transformer and opens the second switch A2. Using the distribution network self-healing function (such as power failure opening), it completes the disconnection of the first switch A1. Furthermore, in this scenario, the first switch A1 should be configured to block the power-on closing function. Specifically, in the event of a fault, the fiber optic differential protection is used to close the TBS switch, causing the substation-side internal switch CB and the second switch A2 to trip, and the first switch A1 to de-energize and open. Simultaneously, the energizing and closing function of the first switch A1 is blocked due to the operation of the fiber optic differential protection, etc. After the blocking, a delay is made to confirm that the fault isolation is complete, and the substation-side internal switch CB is reclosed. After the substation-side internal switch CB is successfully reclosed, it is also necessary to verify whether the energizing conditions of the bypass switch A3 are met by checking the electrical quantity characteristics, such as whether the bypass switch A3 has voltage on the substation side and no voltage or current on the user side, to avoid the risk of asynchronous grid connection. Under the condition that the second grid meets the energizing conditions, the bypass switch A3 is closed to form a temporary bypass power supply path to ensure continuous power supply to the load.

[0103] For example, when the unified power flow controller malfunctions, the isolation of the series feeder from the series transformer is achieved by controlling the first switch A1 and the second switch A2 to open, and the isolation of the series transformer from the series-side converter is achieved by controlling the TBS switch. When the voltage on the load side of the bypass switch A3 drops to a preset voltage threshold, or the current on the load side of the bypass switch A3 drops to a preset current threshold, or both the voltage and current on the load side of the bypass switch A3 drop to the preset voltage threshold, it is determined that the second power grid has lost voltage. When the voltage on the substation side of the bypass switch A3 recovers to the preset voltage threshold range, it is determined that the substation side of the bypass switch A3 has the conditions for power supply. Specifically, the conditions for power supply are that both the first switch A1 and the second switch A2 are in the open state, the voltage on the substation side of the bypass switch A3 is within the preset voltage range, and it is determined that the second power grid has lost voltage. When the conditions for power supply are met, the bypass switch A3 is closed to restore power to the second power grid, avoiding power outages and ensuring the reliability of high-voltage distribution network line operation through rapid power restoration.

[0104] In some embodiments, the unified power flow controller further includes: an optical fiber communication detection module; the optical fiber communication detection module is used to close the TBS switch through the relay protection device when a fault is detected in the unified power flow controller, and to detect the status of the optical fiber communication link between the first switch A1, the second switch A2 and the substation-side internal switches in real time.

[0105] The unified power flow controller is used to generate a third fault switching command and send it to the relay protection device based on the fault status of the unified power flow controller and the status of the optical fiber communication link when the optical fiber communication link is in normal communication status.

[0106] The third fault switching command is configured after the relay protection device, which controls the substation side switch, the first switch A1 and the second switch A2 to exchange fault electrical quantity information in sequence, determine the fault section, and perform the opening operation of the first switch A1 and the second switch A2 according to the fault section, and perform the closing operation of the bypass switch A3 to form the bypass branch mode.

[0107] This application fully utilizes the self-healing function of the distribution network to achieve rapid isolation of fault points in series transformers. The selected technology should fully utilize the characteristics of the fault process to ensure selectivity, speed, reliability, and sensitivity. For example, in accordance with the requirement of rapidly isolating fault points and reducing the number of circuit breaker trips in related substations, the fast-acting intelligent distributed self-healing function meets the requirements.

[0108] The fiber optic communication detection module can monitor the rapid information exchange between all terminals along the entire line. When a fault is detected in the unified power flow controller, the module initiates a self-test of fiber optic communication across all terminals (within 10ms). If communication is normal, distributed detection logic is activated. This logic uses voltage, current, and switch status data uploaded by each terminal to locate the fault section in real time through multi-point collaborative analysis. Specifically, it controls the substation-side switches CB, A1, and A2 to sequentially exchange fault electrical quantity information. For example, if switch CB and A1 simultaneously detect a fault, the fault point is determined to be on the transformer side connected to switch A1, and switch CB remains stationary. Switch A1 then exchanges fault electrical quantity information with A2. If no fault is detected on the load side of switch A2, the fault point is determined to be between A1 and A2, and switch A1 trips to clear the fault. Meanwhile, the energized closing function of the first switch A1 should be locked according to certain logic to ensure that the system is in a stable state before the bypass branch is put into operation; the second switch A2 opens and locks the closing function to achieve fault isolation, and then automatically closes the bypass switch A3. If communication is abnormal, a backup strategy should be considered, that is, a local fault isolation control logic that does not rely on fiber optic communication.

[0109] For example, when the unified power flow controller is faulty, isolation is achieved using series transformer TBS protection and distribution network self-healing function modules. The series transformer TBS protection isolates the converter from the series transformer, specifically by detecting whether the electrical quantity of the series transformer reaches a preset action threshold. When the electrical quantity reaches the preset action threshold, the TBS switch is turned on. The line self-healing function isolates the series-side line from the series transformer, using automated devices or systems to control the first switch A1 and the second switch A2 to trip. Fiber optic communication self-tests are performed on the first switch A1, the second switch A2, and the substation switches. If the fiber optic communication self-test result indicates a communication interruption, the system switches to local fault isolation control logic that does not rely on fiber optic communication, isolating the series transformer and performing bypass closing to restore power supply. If the fiber optic communication self-test result indicates normal communication, the substation switches communicate with the first switch A1 and the second switch A2. Switch A1 and the second switch A2 sequentially exchange fault information to locate the fault section between the first switch A1 and the second switch A2; control the opening and closing of the first switch A1 and the opening and closing of the second switch A2 to isolate the series transformer from the fault; determine whether the second power grid has lost voltage; when the voltage on the load side of bypass switch A3 drops to a preset voltage threshold, or the current on the load side of bypass switch A3 drops to a preset current threshold, or both the voltage and current on the load side of bypass switch A3 drop to the preset voltage threshold, it is determined that the second power grid has lost voltage; when the voltage on the substation side of bypass switch A3 is within the preset voltage threshold range, it is determined that the substation side of bypass switch A3 has the conditions for power supply; when the second power grid has lost voltage and the substation side of bypass switch A3 has the conditions for power supply, control the closing of bypass switch A3 to restore power supply to the second power grid.

[0110] In some embodiments, the second power grid is electrically connected to a backup power ring network line and a power switching module. The power switching module is electrically connected to the backup power ring network line and the unified power flow controller, respectively. The power switching module is used to switch to the backup power ring network line to supply power to the second power grid when the second power grid is disconnected from the first power grid.

[0111] Understandably, by integrating a backup power ring network and power switching module into the second power grid design, power supply continuity and system resilience can be significantly improved. Especially when the main power grid experiences prolonged power outages due to faults or maintenance, the backup power ring network can seamlessly take over load power, preventing production interruptions or data loss. The power switching module employs a millisecond-level response mechanism, combined with dual criteria of voltage dips and frequency offsets, ensuring a seamless and impact-free switching process. Once the fault in the unified power flow controller is cleared, the system switches back to normal power supply from the main power grid.

[0112] like Figure 6As shown in the embodiments of this application, a control method applied to the above-mentioned unified power flow controller is also provided, the method comprising:

[0113] Step S1: Detect the operating status of the unified power flow controller;

[0114] Step S2: When the unified power flow controller is in normal operation, the control switch module executes the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid.

[0115] Step S3: When the unified power flow controller is in a fault state, the control switch module is switched from the series branch mode to the bypass branch mode; wherein, the bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0116] In some embodiments, the unified power flow controller includes a back-to-back converter module, which includes a series-side converter and a parallel-side converter. The series-side converter and the parallel-side converter are connected in parallel and are both connected to the same DC bus. The DC bus is electrically coupled to the energy storage device module through a chopper.

[0117] In some embodiments, the unified power flow controller includes a parallel feeder unit, which includes a parallel transformer. One end of the parallel transformer is electrically connected to the parallel side of the back-to-back converter module, and the other end of the parallel transformer is electrically connected to the substation bus of the first power grid.

[0118] In some embodiments, the switch module includes a first switch, a second switch, and a bypass switch, and the first power grid is connected in series with the second power grid through the first switch and the second switch to form a series feeder;

[0119] One end of the bypass switch is connected to the substation side of the first switch, and the other end of the bypass switch is connected to the load side of the second switch.

[0120] A series transformer is connected between the first switch and the second switch.

[0121] In some embodiments, the switching module further includes a third switch and a TBS switch, the back-to-back converter module is electrically connected to the third switch, the third switch is bypassed to the TBS switch, and the TBS switch is electrically connected to the series transformer.

[0122] In some embodiments, the energy storage device module is provided with a power expansion interface for electrical connection to an external power supply of the unified power flow controller.

[0123] In some embodiments, the unified power flow controller further includes a relay protection device; the relay protection device is electrically connected to the series transformer and the switching module respectively; the control method includes:

[0124] The first current differential signal at both ends of the series transformer is detected in real time by the series transformer. When the first current differential signal is abnormal, a first fault switching command is generated and sent to the relay protection device.

[0125] The first fault switching command is configured after the relay protection device, which controls the tripping of the first switch, the second switch and the third switch, and closes the bypass switch to form a bypass branch mode when the second power grid meets the power supply conditions.

[0126] In some embodiments, the unified power flow controller further includes: a fiber optic differential protection device; the fiber optic differential protection device is installed between the load side of the second switch and the second power grid; a relay protection device is electrically connected to the fiber optic differential protection device; the control method includes:

[0127] The fiber optic differential protection device connects the current differential signal of the feeder in real time, and when the current differential signal is abnormal, it generates a second fault switching command and sends it to the relay protection device.

[0128] After the second fault switching command is configured on the relay protection device, the TBS switch is closed, the second switch, the substation-side internal switch and the first switch are tripped, and the substation-side internal switch is reclosed after a delay. After the substation-side internal switch is reclosed, and under the condition that the second power grid meets the power supply requirements, the bypass switch is closed to form a bypass branch mode.

[0129] In some embodiments, the unified power flow controller further includes: an optical fiber communication detection module;

[0130] The control method includes:

[0131] When a fault is detected in the unified power flow controller, the fiber optic communication detection module closes the TBS switch through the relay protection device and monitors the status of the fiber optic communication link between the first switch, the second switch, and the substation-side switches in real time.

[0132] When the fiber optic communication link is in normal communication status, the unified power flow controller generates a third fault switching command based on the fault status of the unified power flow controller and the fiber optic communication link status and sends it to the relay protection device.

[0133] The third fault switching command is configured after the relay protection device, which controls the substation side switch, the first switch and the second switch to exchange fault electrical quantity information in sequence, determine the fault section, and perform the opening operation of the first switch and the second switch according to the fault section, and perform the closing operation of the bypass switch to form the bypass branch mode.

[0134] The control method of the unified power flow controller proposed in this application will be specifically described below with a specific embodiment.

[0135] (1) Under the normal state of the unified power flow controller, the first switch and the second switch are closed, the bypass switch is open, the series transformer is connected to the feeder, and the power flow distribution is adjusted in real time through the back-to-back converter module.

[0136] (2) Under the fault state of the unified power flow controller, the relay protection device initiates the fault isolation and power restoration process based on the fault information uploaded by the fiber optic differential protection device or the fiber optic communication detection module.

[0137] Specifically, when the unified power flow controller malfunctions, the first and second switches are opened to isolate the series feeder from the series transformer, and the TBS switch or the third switch is used to isolate the series transformer from the series-side converter. When the voltage on the load side of the bypass switch drops to a preset voltage threshold, or the current on the load side of the bypass switch drops to a preset current threshold, or both the voltage and current on the load side of the bypass switch drop to the preset voltage threshold, the second power grid is deemed to have lost voltage. When the voltage on the substation side of the bypass switch recovers to the preset voltage threshold range, the substation side of the bypass switch is deemed to have the conditions for power transmission. The specific conditions for power transmission are that both the first and second switches are open, the voltage on the substation side of the bypass switch is within the preset voltage range, and the second power grid is deemed to have lost voltage. When the conditions for power transmission are met, the bypass switch is closed to restore power to the second power grid, avoiding power outages and ensuring the reliability of high-voltage distribution network line operation through rapid power restoration.

[0138] When the unified power flow controller is faulty, isolation is achieved using series transformer TBS protection and distribution network self-healing module. The series transformer TBS protection isolates the converter from the series transformer by detecting whether the electrical quantity of the series transformer reaches a preset action threshold. When the electrical quantity reaches the preset action threshold, the TBS switch is turned on. The line self-healing function isolates the series-side line from the series transformer, using automated devices or systems to control the first and second switches to trip. Fiber optic communication self-tests are performed on the first and second switches and the substation switches. If the fiber optic communication self-test result indicates communication interruption, the system switches to local fault isolation control logic that does not rely on fiber optic communication, isolating the series transformer and performing bypass closing to restore power supply. If the fiber optic communication self-test result indicates normal communication, the substation switches communicate with the first and second switches. The first and second switches sequentially exchange fault information to locate the fault section between the first and second switches; control the opening and closing of the first switch and lock it in place; control the opening and closing of the second switch and lock it in place to isolate the series transformer from the fault; determine whether the second power grid has lost voltage; when the voltage on the load side of the bypass switch drops to a preset voltage threshold, or the current on the load side of the bypass switch drops to a preset current threshold, or both the voltage and current on the load side of the bypass switch drop to the preset voltage threshold, it is determined that the second power grid has lost voltage; when the voltage on the substation side of the bypass switch is within the preset voltage threshold range, it is determined that the substation side of the bypass switch has the conditions for power supply; when the second power grid has lost voltage and the substation side of the bypass switch has the conditions for power supply, control the bypass switch to close and restore power to the second power grid.

[0139] It should be noted that, by connecting the back-to-back converter module to the energy storage device module, the requirements of the unified power flow controller on the external power supply are reduced in terms of voltage and power flow regulation functions. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuation scenarios. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from the series branch mode to the bypass branch mode when the unified power flow controller is in a fault state. This allows the unified power flow controller in a fault state to be quickly isolated from the series feeder and the first grid to be bypassed to the second grid. Thus, while effectively isolating the faulty controller, it ensures that the power supply to the second grid is not interrupted, realizes fault self-healing and zero-sensory power supply switching, and avoids the problem that the failure of the unified power flow controller will directly cause the corresponding line to lose voltage. It can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios.

[0140] like Figure 7As shown, this application provides an electronic device 10, which includes a memory 20 and a processor 30. The memory 20 stores a computer program. When the computer program is executed by the processor 30, the processor 30 performs the following steps:

[0141] Detect the operating status of the unified power flow controller;

[0142] When the unified power flow controller is in normal operation, the control switch module executes the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid;

[0143] When the unified power flow controller is in a fault state, the control switch module is switched from the series branch mode to the bypass branch mode. The bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0144] This application embodiment reduces the requirements of the unified power flow controller on external power supply in terms of voltage and power flow regulation by connecting back-to-back converter modules to energy storage devices. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuations. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from series branch mode to bypass branch mode in the case of a unified power flow controller failure. This allows for rapid isolation of the unified power flow controller in the series feeder and bypass connection between the first grid and the second grid. Thus, while effectively isolating the faulty controller, it ensures uninterrupted power supply to the second grid, achieving fault self-healing and zero-sensory power supply switching. It avoids the problem of voltage loss of the corresponding line caused by the failure of the unified power flow controller, which can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios.

[0145] This application provides a computer-readable storage medium storing a computer program thereon, which, when executed, performs the following steps:

[0146] Detect the operating status of the unified power flow controller;

[0147] When the unified power flow controller is in normal operation, the control switch module executes the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid;

[0148] When the unified power flow controller is in a fault state, the control switch module is switched from the series branch mode to the bypass branch mode. The bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0149] This application embodiment reduces the requirements of the unified power flow controller on external power supply in terms of voltage and power flow regulation by connecting back-to-back converter modules to energy storage devices. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuations. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from series branch mode to bypass branch mode in the case of a unified power flow controller failure. This allows for rapid isolation of the unified power flow controller in the series feeder and bypass connection between the first grid and the second grid. Thus, while effectively isolating the faulty controller, it ensures uninterrupted power supply to the second grid, achieving fault self-healing and zero-sensory power supply switching. It avoids the problem of voltage loss of the corresponding line caused by the failure of the unified power flow controller, which can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios.

[0150] This application provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer performs the following steps:

[0151] Detect the operating status of the unified power flow controller;

[0152] When the unified power flow controller is in normal operation, the control switch module executes the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid;

[0153] When the unified power flow controller is in a fault state, the control switch module is switched from the series branch mode to the bypass branch mode. The bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

[0154] This application embodiment reduces the requirements of the unified power flow controller on external power supply in terms of voltage and power flow regulation by connecting back-to-back converter modules to energy storage devices. It can provide rapid voltage and frequency support to the second grid under external disturbances and related new energy fluctuations. At the same time, by designing the switching module in the series feeder unit, the switching module can switch from series branch mode to bypass branch mode in the case of a unified power flow controller failure. This allows for rapid isolation of the unified power flow controller in the series feeder and bypass connection between the first grid and the second grid. Thus, while effectively isolating the faulty controller, it ensures uninterrupted power supply to the second grid, achieving fault self-healing and zero-sensory power supply switching. It avoids the problem of voltage loss of the corresponding line caused by the failure of the unified power flow controller, which can meet the high reliability operation requirements of high-voltage distribution networks and is conducive to the large-scale promotion of efficient power flow regulation technology in distribution network scenarios.

[0155] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0156] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0157] In the embodiments provided by this invention, it should be understood that the disclosed electronic devices, computer storage media, computer program products, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0158] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0159] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0160] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for executing all or part of the steps of the methods described in the various embodiments of the present invention through a computer device (which may be a personal computer, a server, or a network device, etc.). The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0161] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A unified power flow controller, wherein the unified power flow controller is installed between a first power grid and a second power grid, characterized in that, include: Back-to-back converter modules, energy storage modules, parallel feeder units, and series feeder units; The energy storage device module is electrically connected to the DC side of the back-to-back converter module; the energy storage device module is used to provide frequency and voltage support to the second power grid through the back-to-back converter module. The back-to-back converter module is electrically connected to the transformer station bus of the first power grid through the parallel feeder unit; The series feeder unit includes a series transformer and a switch module; the back-to-back converter module is electrically connected to the series transformer, the series transformer is electrically connected to the switch module, and the first power grid is electrically connected to the access point of the second power grid through the switch module; The switching module is used to switch from series branch mode to bypass branch mode in response to the fault state of the unified power flow controller; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid, and the bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

2. The unified power flow controller according to claim 1, characterized in that, The back-to-back converter module includes a series-side converter and a parallel-side converter. The series-side converter and the parallel-side converter are connected in parallel. Both the series-side converter and the parallel-side converter are connected to the same DC bus. The DC bus is electrically coupled to the energy storage device module through a chopper.

3. The unified power flow controller according to claim 1, characterized in that, The parallel feeder unit includes a parallel transformer. One end of the parallel transformer is electrically connected to the parallel side of the back-to-back converter module, and the other end of the parallel transformer is electrically connected to the substation bus of the first power grid.

4. The unified power flow controller according to claim 1, characterized in that, The switch module includes a first switch, a second switch, and a bypass switch. The first power grid is connected in series with the second power grid through the first switch and the second switch to form the series feeder. One end of the bypass switch is connected to the substation side of the first switch, and the other end of the bypass switch is connected to the load side of the second switch. The series transformer is connected between the first switch and the second switch.

5. The unified power flow controller according to claim 4, characterized in that, The switch module also includes a third switch and a TBS switch. The back-to-back converter module is electrically connected to the third switch, the third switch is bypassed to the TBS switch, and the TBS switch is electrically connected to the series transformer.

6. The unified power flow controller according to claim 1, characterized in that, The energy storage device module is equipped with a power expansion interface, which is used for electrical connection with the external power supply of the unified power flow controller.

7. The unified power flow controller according to claim 5, characterized in that, It also includes a relay protection device; the relay protection device is electrically connected to the series transformer and the switch module respectively; The series transformer is used to detect the first current differential signal at both ends of the series transformer in real time. When the first current differential signal is abnormal, a first fault switching command is generated and sent to the relay protection device. After the first fault switching command is configured on the relay protection device, it controls the tripping of the first switch, the second switch and the third switch, and closes the bypass switch when the second power grid meets the power supply conditions, thus forming the bypass branch mode.

8. The unified power flow controller according to claim 7, characterized in that, Also includes: Fiber optic differential protection device; The fiber optic differential protection device is installed between the load side of the second switch and the second power grid; the relay protection device is electrically connected to the fiber optic differential protection device. The fiber optic differential protection device is used to detect the second current differential signal of the series feeder in real time, and when the second current differential signal is abnormal, it generates a second fault switching command and sends it to the relay protection device. After the second fault switching command is configured on the relay protection device, the TBS switch is closed, the second switch, the substation-side internal switch and the first switch are tripped, the substation-side internal switch is reclosed after a delay, and after the substation-side internal switch is reclosed, and the bypass switch is closed under the condition that the second power grid meets the power supply requirements, thus forming the bypass branch mode.

9. The unified power flow controller according to claim 7, characterized in that, Also includes: Fiber optic communication detection module; The fiber optic communication detection module is used to close the TBS switch through the relay protection device when a fault is detected in the unified power flow controller, and to detect the status of the fiber optic communication link between the first switch, the second switch and the substation-side switch in real time. The unified power flow controller is used to generate a third fault switching command and send it to the relay protection device based on the fault status of the unified power flow controller and the status of the optical fiber communication link when the optical fiber communication link is in normal communication status. The third fault switching command is configured after the relay protection device, which controls the substation-side internal switch, the first switch and the second switch to exchange fault electrical quantity information in sequence, determine the fault range, and perform the opening operation of the first switch and the second switch according to the fault range, and perform the closing operation of the bypass switch to form the bypass branch mode.

10. A control method applied to a unified power flow controller as described in any one of claims 1 to 9, characterized in that, The method includes: Detect the operating status of the unified power flow controller; When the unified power flow controller is in normal operating state, it controls the switch module to execute the series branch mode; wherein, the series branch mode is used to connect the unified power flow controller in series to the series feeder between the first power grid and the second power grid; When the unified power flow controller is in a fault state, the switching module is controlled to switch from the series branch mode to the bypass branch mode; wherein, the bypass branch mode is used to isolate the unified power flow controller in the fault state from the series feeder and to bypass the first power grid and the second power grid.

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