Flexible interconnection device and multifunctional integrated movable multi-port flexible interconnection equipment

Abstract

The invention provides a flexible interconnection device. The flexible interconnection device comprises a multi-winding self-coupling transformer and a power electronic converter, the multi-winding self-coupling transformer comprises a main winding and a plurality of auxiliary windings; the main winding is connected in series with an output port of the power electronic converter; the auxiliary winding is connected with an input port of the power electronic converter; the power electronic converter comprises a plurality of cascade units, and each cascade unit comprises a plurality of AC-AC conversion cascade sub-modules. And one end of the output port of each cascade unit is connected to the feeder line, and the other end of the output port is directly connected with the main winding to form series configuration between the two feeder lines. Meanwhile, the invention provides multifunctional integrated movable multi-port flexible interconnection equipment based on the flexible interconnection device, a control method and application. According to the flexible interconnection device, the low-cost, compact and movable design is achieved, ports are easy to expand, multifunctional integration and high-efficiency conversion are achieved, the size is reduced, vehicle-mounted movement is achieved, and the flexible interconnection device is provided with an emergency vehicle and an energy storage access port.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology. Specifically, it relates to a flexible interconnection device and a multifunctional integrated movable multi-port flexible interconnection device with multi-port easy expansion, compact design, and multifunctional integration based on the flexible interconnection device, as well as its control method and application. Background Art

[0002] With the continuous development of the power system and the rapid growth of user loads, the distribution network is facing increasingly severe challenges. The existing radial long-line distribution scheme conflicts with the high-quality power supply requirements of users under the high-speed economic development, becoming a bottleneck restricting the high-quality development of the distribution network. For the upgrade and transformation of the distribution network, there are currently three typical solutions: The first is the capacity expansion and extension of the distribution network. By increasing the capacity of the distribution network, its power supply capacity is directly improved to meet the needs of the rapid growth of large-scale user loads and improve the power quality on the user side. However, this solution is limited by the tight land area or complex and changeable terrain in some areas. It has a large floor area and high construction costs, and the distribution network still lacks effective regulation means. The second is the energy storage configuration scheme. By the active power regulation and peak shaving and valley filling capabilities of energy storage, the voltage quality and power supply reliability on the user side are improved, and certain regulation means are provided. However, energy storage devices usually have safety hazards and high costs, which limit their wide promotion and application. The third is the flexible interconnection scheme. By interconnecting multiple distribution feeders through power electronic devices, flexible power flow control, load transfer, and local reactive power compensation between feeders are realized, effectively solving the problems of long-line overload and low voltage, thereby realizing the dynamic capacity increase of feeders and the optimal allocation of power resources.

[0003] However, existing flexible interconnection devices have drawbacks such as high device cost, low power density and efficiency, being bulky and immovable, having low utilization rate in conventional power usage scenarios, and being able to achieve spatial energy allocation only at one or several nodes of the distribution network. However, the functional requirements of the distribution network in many areas vary seasonally. Only during some periods is flexible interconnection equipment needed for regulation, resulting in low utilization rate of the installed equipment. The distribution network without installed flexible interconnection equipment also needs seasonal adjustment, consuming a large amount of manpower and material resources. The existing devices are immovable and difficult to meet the regulation requirements in terms of time, causing waste of resources. Therefore, it is difficult to achieve low-cost and large-scale application of the equipment in the distribution network. At the same time, existing devices usually focus on a single function, such as load transfer, reactive power compensation or power flow control, etc., lacking flexible multi-functional integration capabilities. When facing increasingly complex grid requirements, they cannot adapt to the conversion and coordination requirements of multiple working modes. In addition, the port expandability of existing devices is poor. Once new functions or ports need to be added, the entire full-power converter must be installed, significantly increasing the equipment cost and restricting its flexibility. Especially in areas with rapidly changing power usage demands, adding new ports often requires huge capital investment and a long equipment update cycle, seriously restricting the development of the distribution network. Existing flexible interconnection equipment cannot achieve flexible and convenient deployment and adjustment, and is difficult to be applied at low cost and on a large scale.

[0004] At the same time, there will be different operation regulation requirements in the complex scenarios of the distribution network. For example, there is a need for multi-line connection of power supply vehicles for emergency power supply under disasters such as typhoons on coastal lines, a need for multi-line combined power supply in large-capacity DC supercharging stations, and a need for energy storage to cooperate with flexible interconnection to achieve high-quality and reliable power supply in important industrial and commercial parks, etc. Therefore, there is an urgent need in this field for an integrated design technology of flexible interconnection and the above functions, so as to promote the large-scale application of flexible interconnection technology in the distribution network and improve the overall operation level of the distribution network. At present, no description or report of similar technologies to the present invention has been found, and no similar materials at home and abroad have been collected. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a flexible interconnection device, a multi-functional integrated movable multi-port flexible interconnection device, its control method and application.

[0006] According to one aspect of the present invention, a flexible interconnection device is provided, including: a transformer and a power electronic converter connected to each other; wherein:

[0007] The primary side of the transformer is connected to the input end of the power electronic converter, and the secondary side of the transformer is connected in series with the output end of the power electronic converter to form a series-parallel type power flow controller structure and provide an input voltage for the power electronic converter;

[0008] The power electronic converter includes a plurality of series-connected power electronic cascaded units and forms two AC ports for adjusting and implementing feeder power flow control; one of the AC ports is connected to the transformer; the other AC port is used to output a series voltage to continuously adjust the line power flow, forming a series configuration between two feeders.

[0009] Preferably, the above flexible interconnection device further includes: selecting one feeder as the active power balance feeder; the active power of the balance feeder is automatically balanced according to the distribution of line active power.

[0010] According to another aspect of the present invention, there is provided a multifunctional integrated mobile multi-port flexible interconnection device, characterized in that it includes the above flexible interconnection device of the present invention, as well as a plurality of AC ports, a plurality of DC ports provided on the flexible interconnection device, and an access port for connecting an emergency power supply device and an energy storage device; wherein:

[0011] Each of the AC ports has a different voltage level, and all AC ports perform power flow decoupling control through the flexible interconnection device;

[0012] Each of the DC ports has a different voltage level, and all DC ports perform voltage control through the flexible interconnection device.

[0013] According to a third aspect of the present invention, there is provided a control method for a multifunctional integrated mobile multi-port flexible interconnection device. When the transformer of the flexible interconnection device adopts a multi-winding autotransformer and the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, it is used to achieve the internal energy balance of the multifunctional integrated mobile multi-port flexible interconnection device, including:

[0014] The internal energy balance of the multifunctional integrated mobile multi-port flexible interconnection device is manifested as the capacitor voltage of the DC bus remains stable, which requires that the active power flowing into the capacitor of the DC bus remains zero; by adjusting the voltage of the balance port and the difference in current at the two taps of the auxiliary winding, that is, the amplitude and magnitude of the differential mode current, the internal energy balance of the multi-winding autotransformer is achieved.

[0015] According to a fourth aspect of the present invention, there is provided another control method for a multifunctional integrated mobile multi-port flexible interconnection device. When the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, it is used to achieve the reactive power compensation of the balance feeder of the multifunctional integrated mobile multi-port flexible interconnection device, including:

[0016] According to the magnetic potential balance of the transformer, when the primary winding of the transformer is connected to the power supply, magnetic flux will be generated in the magnetic circuit, and induced electromotive forces will be induced in the primary and secondary windings to balance the power supply voltage. When the change in the power supply voltage is less than the set threshold, the magnetic flux in the magnetic circuit remains unchanged; after connecting the load, there is current flowing through the secondary winding, which will also generate magnetic potential and affect the magnetic flux in the magnetic circuit, thereby affecting the values of the induced electromotive forces in the primary and secondary windings; when the magnetic flux in the magnetic circuit changes, since the power supply voltage remains unchanged, the current in the primary winding will automatically change to keep the magnetic flux in the magnetic circuit unchanged, and the change in the current in the primary winding causes a change in the magnetic potential in the magnetic circuit, which basically compensates for the influence of the load change in the secondary winding on the magnetic flux in the magnetic circuit; at this time, the change in the current in the secondary winding affects the current in the line at the head end of the transformer.

[0017] According to the relationship between the differential-mode current and the current in the line at the head end, the reactive power at the head end is controlled by controlling the differential-mode current; since both the energy balance and the reactive power balance of the feeder are controlled by the full-bridge cascaded sub-module, at this time, on the premise of ensuring the energy balance of the flexible interconnection device, a reactive power compensation device is connected to other auxiliary windings to achieve the decoupled control of the power flow of all feeders.

[0018] According to the fifth aspect of the present invention, an emergency power supply vehicle is provided, which adopts the above-mentioned multifunctional integrated movable multi-port flexible interconnection device of the present invention, and connects the multifunctional integrated movable multi-port flexible interconnection device to the emergency power supply device through the emergency power supply device connection port, and is used to realize the joint power supply of multiple feeders in an emergency scenario.

[0019] Due to the adoption of the above technical solutions, compared with the prior art, the present invention has at least one of the following beneficial effects:

[0020] Compared with the existing flexible interconnection equipment, the present invention optimizes the power electronic module, reduces the number of power devices and capacitors, thereby significantly reducing the manufacturing cost of the equipment. The present invention greatly reduces the usage amount of core components, is easy to expand ports, realizes high-cost-effective flexible interconnection control, and greatly increases the economic applicability of the equipment. And the present invention has a small volume and lightweight characteristics, can be realized for vehicle-mounted movement, is convenient for transportation and rapid deployment, and is especially suitable for emergency scenarios or power grid application scenarios in mountain villages and remote areas.

[0021] The present invention can realize the power flow regulation, reactive power compensation, DC microgrid access and flexible energy storage integration functions of multiple lines by simply transforming the existing transformer, and has the characteristics of easy implementation, simple operation, easy port expansion, comprehensive functions, low cost and small volume.

[0022] The present invention can design an emergency power supply vehicle access port and an energy storage system mounting port, so as to quickly access an emergency power source or an energy storage system when a failure occurs in the distribution network or the load demand suddenly increases, realize the emergency power supply guarantee for important loads, and flexibly adjust the system power.

[0023] The present invention realizes the low-cost, compact, movable design, easy-to-expand ports, multi-functional integration and high-efficiency conversion of the flexible interconnection device, reduces the equipment volume for vehicle-mounted movement, and has emergency vehicle and energy storage access ports.

[0024] The present invention is applicable to the distribution network occasion, replaces the traditional flexible interconnection device that is immovable and single-functional, meets the flexible interconnection of AC and DC feeders at multiple levels and the access requirements of various types of power sources and loads, improves the power quality and power supply reliability of the distribution network, realizes the high utilization rate and multi-functional integration of the device, and has the multi-feeder emergency power supply capacity after accessing the emergency power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects and advantages of the present invention will become more apparent:

[0026] Figure 1 It is a schematic diagram of the functional application of a multi-functional integrated movable multi-port flexible interconnection device in an embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of the topological structure of a flexible interconnection device and its system for realizing the control of multiple feeders in an embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram of the structure of a cascade unit in a preferred embodiment of the present invention.

[0029] Figure 4 It is a schematic diagram of a typical topology example of sub-modules in a cascade unit in a preferred embodiment of the present invention.

[0030] Figure 5 It is a block diagram of the topological structure of a dual-port electromagnetic coupling type flexible interconnection device and its control method for realizing the power flow control of three feeders in Specific Application Example 1;

[0031] Figure 6 It is a schematic diagram of the topological structure of a dual-port electromagnetic coupling type flexible interconnection device and its system with an auxiliary winding connected to a reactive power compensation device in Specific Application Example 2;

[0032] Figure 7 It is a schematic diagram of the topological structure of a dual-port electromagnetic coupling type flexible interconnection device and its system with an auxiliary winding connected to an emergency power supply vehicle through an AC-AC converter in Specific Application Example 3.

[0033] Figure 8 It is a schematic diagram of the topological structure of the dual-port electromagnetic coupling type flexible interconnection device in Specific Application Example 4 and the system where its auxiliary winding is connected to multiple energy storage devices through multiple AC-DC converters.

[0034] Figure 9 It is a schematic diagram of the topological structure of the dual-port electromagnetic coupling type flexible interconnection device in Specific Application Example 5 and the system where its auxiliary winding is connected to a DC microgrid with multiple voltage levels through multiple AC-DC converters. Specific embodiments

[0035] The embodiments of the present invention will be described in detail below: These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

[0036] In order to achieve low cost, compactness, portable design, easy port expansion, multi-functional integration and high-efficiency conversion, reduce the equipment volume for on-vehicle mobility, and have emergency vehicle and energy storage access ports, be applicable to the distribution network scenario, replace the traditional immobile and single-function flexible interconnection device, meet the flexible interconnection of AC-DC feeders with multiple levels and the access requirements of various types of sources and loads, improve the power quality and power supply reliability of the distribution network, realize the high utilization rate and multi-functional integration of the device, and have the multi-feeder emergency power supply capacity after connecting the emergency power supply, the embodiments of the present invention provide a flexible interconnection device, and based on this flexible interconnection device, a multi-functional integrated portable multi-port flexible interconnection device and its control method and application can be realized.

[0037] Specifically, as Figure 2 shown, in one embodiment, the provided flexible interconnection device may include: a transformer and a power electronic converter connected to each other; wherein:

[0038] The primary side of the transformer is connected to the input end of the power electronic converter, and the secondary side of the transformer is connected in series with the output end of the power electronic converter, forming a series-parallel type power flow controller structure and providing an input voltage for the power electronic converter;

[0039] The power electronic converter includes multiple series-connected power electronic cascade units and forms two AC ports for adjusting and realizing feeder power flow control; one of the AC ports is connected to the transformer; the other AC port is used to output a series voltage to continuously adjust the line power flow, forming a series configuration between two feeders.

[0040] In some preferred embodiments, the transformer is a multi-winding autotransformer, including: a main winding and multiple auxiliary windings; the main winding is connected to one end of the output port of the power electronic converter to form an autotransformer structure; the multiple auxiliary windings are connected to the input port of the power electronic converter to form a series-parallel type power flow controller structure and provide the input voltage for the power electronic converter.

[0041] The power electronic converter includes multiple series-connected power electronic cascaded units and forms two AC ports for adjusting and realizing feeder power flow control; one of the AC ports is connected to the auxiliary winding of the transformer to form a parallel side; the other AC port is connected to the primary side of the transformer at one end and to the feeder at the other end to form a series configuration between two feeders, and can output a continuously adjustable series voltage to control the line power flow.

[0042] In some preferred embodiments, the number of auxiliary windings of the multi-winding autotransformer is jointly determined by the number of connected feeders and the number of cascaded units.

[0043] In some preferred embodiments, as Figure 3 and Figure 4 shown, each cascaded unit includes multiple cascaded sub-modules for realizing different functions; each cascaded sub-module includes two AC ports; one of the AC ports is connected to an auxiliary winding of the transformer to become an input port; the other AC port is cascaded with other cascaded sub-modules in the same cascaded unit and then connected in series with the line to form an adjustable voltage, becoming an output port; one end of the output port is connected to the output port of the upper-level cascaded unit or to the main winding of the transformer, and the other end of the output port is connected to the output port of the lower-level cascaded unit or to the feeder to form a series configuration between two feeders for outputting a series compensation voltage to continuously adjust the line power flow.

[0044] In some preferred embodiments, the cascaded sub-module adopts any one of the following forms:

[0045] - The cascaded sub-module adopts a full-bridge form, where the input port of the full-bridge form is connected to an auxiliary winding or the first winding of the transformer as a balance port to maintain the stability of the internal energy of the cascaded sub-module and adjust the amplitude and phase of the series voltage.

[0046] - The cascaded sub-module adopts a thyristor type step voltage regulator form, and the input port of the thyristor type step voltage regulator form is connected to an auxiliary winding or the first winding of the transformer to adjust the amplitude of the series voltage.

[0047] In some preferred embodiments, the above flexible interconnection device may further include: selecting one feeder as an active power balance feeder; the active power of the balance feeder is automatically balanced according to the distribution of the line active power.

[0048] Based on the flexible interconnection device provided in the above embodiments of the present invention, in another embodiment, a multifunctional integrated movable multi-port flexible interconnection device is provided.

[0049] Specifically, as Figure 1 shown, the multifunctional integrated movable multi-port flexible interconnection device provided in this embodiment may include: the flexible interconnection device in any one of the above embodiments of the present invention, and a plurality of AC ports, a plurality of DC ports, and an access port for connecting an emergency power supply device and an energy storage device provided on the flexible interconnection device; wherein:

[0050] Each AC port has a different voltage level, and all AC ports perform power flow decoupling control through the flexible interconnection device;

[0051] Each DC port has a different voltage level, and all DC ports perform voltage control through the flexible interconnection device.

[0052] In some preferred embodiments, the above multifunctional integrated movable multi-port flexible interconnection device may further include any one or any combination of the following:

[0053] - A reactive power compensation device provided inside the flexible interconnection device; the reactive power compensation device is connected to an auxiliary winding of the transformer in the flexible interconnection device for performing reactive power control on the balanced feeder;

[0054] - An AC-AC converter provided inside the flexible interconnection device; one end of the AC-AC converter is connected to an auxiliary winding of the transformer in the flexible interconnection device; the other end of the AC-AC converter is connected to an AC power source for multi-feeder combined power supply in emergency scenarios;

[0055] - An AC-DC converter provided inside the flexible interconnection device; the AC port of the AC-DC converter is connected to an auxiliary winding of the transformer in the flexible interconnection device; the DC port of the AC-DC converter is connected to a DC microgrid for realizing the application of optical storage direct flexibility; or

[0056] The DC port of the AC-DC converter is connected to a solar photovoltaic or energy storage device for directly consuming new energy power.

[0057] Based on the multifunctional integrated movable multi-port flexible interconnection device provided in the above embodiments of the present invention, the following embodiments of the present invention also implement corresponding control methods and their applications.

[0058] Specifically, in one embodiment, a control method for a multi-functional integrated movable multi-port flexible interconnection device is provided. When the transformer of the flexible interconnection device adopts a multi-winding autotransformer and the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, to achieve the internal energy balance of the multi-functional integrated movable multi-port flexible interconnection device, it may include:

[0059] Express the internal energy balance of the multi-functional integrated movable multi-port flexible interconnection device as the capacitor voltage of the DC bus remaining stable, which requires that the active power flowing into the capacitor of the DC bus remains zero; by adjusting the voltage of the balance port and the amplitude and magnitude of the differential-mode current, that is, the difference in current between the two taps of the auxiliary winding, the internal energy balance of the multi-winding autotransformer is achieved.

[0060] Specifically, in one embodiment, another control method for a multi-functional integrated movable multi-port flexible interconnection device is provided. When the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, to achieve the balance feeder reactive power compensation of the multi-functional integrated movable multi-port flexible interconnection device, it may include:

[0061] According to the magnetic potential balance of the transformer, when the primary winding of the transformer is connected to the power supply, a magnetic flux will be generated in the magnetic circuit, and induced electromotive forces will be induced in the primary and secondary windings to balance the power supply voltage. When the change in the power supply voltage is less than the set threshold, the magnetic flux in the magnetic circuit remains unchanged; after the load is connected, there is a current flowing through the secondary winding, which will also generate a magnetic potential, affecting the magnetic flux in the magnetic circuit, and thus affecting the values of the induced electromotive forces in the primary and secondary windings; when the magnetic flux in the magnetic circuit changes, since the power supply voltage remains unchanged, the current in the primary winding will automatically change to keep the magnetic flux in the magnetic circuit unchanged, and the change in the magnetic potential in the magnetic circuit caused by the change in the primary winding current basically compensates for the influence of the change in the load on the magnetic flux in the magnetic circuit due to the secondary winding; at this time, the change in the current in the secondary winding affects the current in the line at the head end of the transformer;

[0062] According to the relationship between the differential-mode current and the current in the line at the head end, the reactive power at the head end is controlled by controlling the differential-mode current; since both the energy balance and the balance feeder reactive power are controlled by the full-bridge form cascaded sub-module, at this time, on the premise of ensuring the energy balance of the flexible interconnection device, a reactive power compensation device is connected to other auxiliary windings to achieve the decoupled control of the power flow of all feeders.

[0063] In the control methods for the multi-functional integrated movable multi-port flexible interconnection device provided in the above two embodiments, the control system of the power electronic converter may further include:

[0064] Detection circuit, used to detect system variables required by the control system and variable values of the reactive power compensator. Among them, the objects to be detected include: grid voltage, power factor, active component and reactive component of grid current, as well as active component and reactive component of compensator device current;

[0065] Control circuit, used to analyze and process the detected signals, calculate active and reactive power factors by sampling the voltage and current signals of the system, and determine relevant control parameters according to the reference values set by the system;

[0066] Trigger circuit, which emits trigger pulses required for the thyristor trigger angle. The trigger circuit includes a synchronous conversion circuit for processing grid AC signals and an isolation and amplification circuit for pulse signals.

[0067] An embodiment of the present invention also provides an emergency power supply vehicle, which adopts the multifunctional integrated movable multi-port flexible interconnection device provided by the above embodiment of the present invention, and connects the multifunctional integrated movable multi-port flexible interconnection device to the emergency power supply device through the emergency power supply device access port, so as to realize multi-feeder combined power supply in emergency scenarios.

[0068] The multifunctional integrated movable multi-port flexible interconnection device provided by this embodiment:

[0069] 1. It has multiple AC ports;

[0070] Furthermore, the AC ports can have multiple voltage levels;

[0071] Furthermore, the device can achieve power flow decoupling control for all AC ports;

[0072] 2. It has multiple DC ports;

[0073] Furthermore, the DC ports can have multiple voltage levels;

[0074] Furthermore, the device can achieve voltage control for all DC ports;

[0075] 3. It is compactly designed, can be carried by vehicle and moved, and is plug-and-play. It can meet the load transfer of multiple nodes in the distribution network and the power flow regulation requirements between feeders, and improve the utilization rate of the flexible interconnection device;

[0076] Optionally, as an implementation manner of the present invention, a reactive power compensation device is provided inside the device, which can achieve a wider range of reactive power control for the balanced feeder;

[0077] Optionally, as an implementation manner of the present invention, a DC-DC converter is provided inside the device;

[0078] Furthermore, as an implementation manner of the present invention, the DC-DC converter can be connected to the DC microgrid to realize the application of the optical storage DC flexible technology;

[0079] Furthermore, as an implementation manner of the present invention, the DC-DC converter can be connected to a solar photovoltaic or energy storage device to directly consume new energy power.

[0080] Optionally, as an implementation manner of the present invention, the device is connected to an emergency power supply device such as a diesel engine or a battery, etc., to jointly form an emergency power supply vehicle, realizing multi-feeder combined power supply in emergency scenarios.

[0081] The multifunctional integrated movable multi-port flexible interconnection device provided by the above embodiments of the present invention can realize the following application scenarios:

[0082] 1. Power flow control scenario. Based on the flexible interconnection device, the basic topology function of this device is power flow control. It adopts power flow decoupling control and is regulated by a power electronic device, having the ability to flexibly adjust the power distribution between feeders, realizing dynamic load transfer and optimal allocation of power resources;

[0083] 2. Low voltage governance scenario. By controlling the power flow at the port, this device has voltage regulation and stabilization functions to cope with the low voltage problem caused by the long power supply radius of the line, ensuring that the voltage on the user side meets the standard requirements;

[0084] 3. Reactive power compensation scenario. After connecting a reactive power compensation device at the connection between the auxiliary winding and the power electronic converter, this device can provide a wider range of reactive power regulation functions to improve the power factor and reduce system losses;

[0085] 4. Emergency power supply scenario. This device adopts a compact and movable design, having the ability of emergency quick access and power support, and can ensure the continuous power supply of critical loads by accessing an emergency power supply vehicle in case of power interruption or power failure;

[0086] 5. Flexible storage integration scenario. By adding an auxiliary winding and connecting multiple AC-DC converters, the present invention has the ability to seamlessly integrate with the energy storage system. By mounting an energy storage device, it provides stronger dynamic regulation and emergency support capabilities for the power system. Through the regulation ability of the energy storage system, it discharges during the peak power demand period and charges during the low valley period, realizing load balancing, optimizing the allocation of power resources, and reducing the pressure on the distribution network.

[0087] 6. Flexible interconnection scenario between AC lines and DC microgrids. By adding an auxiliary winding and connecting multiple AC-DC converters, it can support the flexible interconnection of AC and DC through multiple AC-DC converters, realizing bidirectional power exchange to meet the requirements in the grid-connected and island modes of the microgrid;

[0088] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the application scenarios implemented in the above-described embodiments of the present invention in combination with specific application examples and the accompanying drawings. Obviously, the drawings in the following description are only one requirement of the present invention. Generally speaking, the present invention not only reduces the floor area of the device, but also reduces the installation and operation costs of the device.

[0089] Specific Application Example 1

[0090] As Figure 5 shown, a device topology and system connection for realizing the decoupled control of the power flow of three feeders are achieved by using a flexible interconnection device, realizing the power flow control scenario.

[0091] This specific application example adopts a self-coupled electromagnetic hybrid cascaded series-regulated flexible interconnection device to form a multifunctional integrated movable multi-port flexible interconnection device. The flexible interconnection device includes a multi-winding self-coupled transformer and a power electronic converter;

[0092] As Figure 2 shown, in this specific application example 1, a self-coupled electromagnetic hybrid cascaded series-regulated flexible interconnection device is provided, including a multi-winding self-coupled transformer and a power electronic converter;

[0093] The multi-winding self-coupled transformer is used to provide a channel for the energy stability of the power electronic converter, and it includes a main winding and three auxiliary windings;

[0094] The main winding and the auxiliary windings are connected through the power electronic converter;

[0095] The auxiliary windings are connected to the power electronic converter;

[0096] Each phase of the power electronic converter consists of three cascaded units, and these cascaded units are all full-bridge back-to-back type sub-modules;

[0097] Furthermore, the full-bridge back-to-back type sub-modules can be divided into an energy balance module and a power flow regulation module according to their functions;

[0098] It should be noted that the AC output port of the power flow regulation sub-module is connected in series with the feeder. By adjusting the amplitude and phase of the voltage at the AC output port of the sub-module connected in series on the feeder, the decoupled control of the active power and reactive power of the feeder is realized;

[0099] It should be noted that the transformer is connected to the energy balance module through the auxiliary winding. The energy balance module shares the same common capacitor with the power flow regulation module to realize the energy stability inside the device.

[0100] The above specific application example 1 combines the advantages of power electronic structures and traditional transformers by adopting a hybrid method of transformers and power electronic topologies. This hybrid design not only simplifies control but also facilitates the expansion of interconnection ports, significantly reducing costs and volume and improving the reliability of the system. More importantly, it realizes continuous decoupling control of the power flow of multiple interconnected feeders, demonstrating excellent power flow regulation capabilities.

[0101] Specific application example 2

[0102] As Figure 6 shown, a flexible interconnection device is used to implement the device topology and system connection for power flow control of two feeders. At the same time, a reactive power compensation device is connected through a transformer to achieve reactive power regulation over the entire range of balanced feeders and power flow decoupling control of all feeders, realizing a reactive power compensation scenario.

[0103] According to the magnetic potential balance of the transformer, when the primary winding of the transformer is connected to the power supply, a magnetic flux will be generated in the magnetic circuit, and induced electromotive forces will be induced in the primary and secondary windings to balance the power supply voltage. When the power supply voltage changes little, the magnetic flux in the magnetic circuit will also remain basically unchanged; after connecting the load, there will be a current flowing through the secondary winding, which will also generate a magnetic potential, affecting the magnetic flux in the magnetic circuit and thus the values of the induced electromotive forces in the primary and secondary windings; when the magnetic flux in the magnetic circuit changes, since the power supply voltage remains unchanged, the current in the primary winding will automatically change to keep the magnetic flux in the magnetic circuit unchanged, and the change in the magnetic potential in the magnetic circuit caused by the change in the primary winding current basically compensates for the influence of the load change in the secondary winding on the magnetic flux in the magnetic circuit; therefore, the change in the current in the secondary winding will affect the current in the line at the head end of the transformer.

[0104] Therefore, according to the relationship between the differential-mode current and the current in the line at the head end, the control of the reactive power at the head end is achieved by controlling the differential-mode current; since both the energy balance and the reactive power of the balanced feeder are controlled by the full-bridge cascaded sub-module, limited by the selection of power electronic devices, it cannot meet the full-power operation conditions of the balanced feeder. Therefore, on the premise of ensuring the energy balance of the device, a reactive power compensation device is connected to other auxiliary windings to achieve power flow decoupling control of all feeders.

[0105] Specific application example 3

[0106] As Figure 7 shown, a flexible interconnection device is used to implement the device topology and system connection for power flow control of two feeders. At the same time, an emergency power supply vehicle is connected through an auxiliary winding and the connected AC-AC converter to achieve mobile multi-feeder combined high-quality power supply, realizing an emergency power supply scenario.

[0107] Specific application example 4

[0108] As Figure 8As shown in the figure, a flexible interconnection device is used to achieve the device topology and system connection for power flow control of two feeders. At the same time, an energy storage device is connected through an auxiliary winding and an AC-DC converter, realizing a movable integrated flexible energy storage equipment. Through the regulation ability of the energy storage system, the power flow regulation in the spatial distribution network can be effectively achieved, the allocation of power resources can be optimized, the flexibility and stability of the distribution network can be improved, and the integrated flexible energy storage scenario can be realized.

[0109] Specific application example 5

[0110] As Figure 9 shown in the figure, a flexible interconnection device is used to achieve the device topology and system connection for power flow control of two feeders. At the same time, a DC microgrid is connected through an auxiliary winding and an AC-DC converter for joint AC-DC regulation and supply. By combining with a photovoltaic power generation and energy storage system, the device can flexibly absorb the electric energy of a DC power source (such as solar power generation), and transmit the power to the load end through a DC flexible interconnection device, realizing the flexible interconnection scenario between an AC line and a DC microgrid.

[0111] Matters not covered in the above embodiments of the present invention are all well-known technologies in the art.

[0112] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific implementation manners, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A flexible interconnection device, characterized in that, Comprising: A transformer and a power electronic converter connected to each other; wherein: The primary side of the transformer is connected to the input end of the power electronic converter, and the secondary side of the transformer is connected in series with the output end of the power electronic converter to form a series-parallel power flow controller structure and provide an input voltage for the power electronic converter; The power electronic converter includes a plurality of series-connected power electronic cascade units and forms two AC ports for adjusting and realizing feeder power flow control; one of the AC ports is connected to the transformer; the other AC port is used for outputting a series voltage to continuously adjust the line power flow and form a series configuration between two feeders.

2. The flexible interconnection device according to claim 1, wherein The transformer adopts a multi-winding autotransformer, including: a main winding and a plurality of auxiliary windings; the main winding is connected to one end of the output port of the power electronic converter to form an autotransformer structure; a plurality of the auxiliary windings are connected to the input port of the power electronic converter; One AC port of the power electronic converter is connected to the auxiliary winding of the multi-winding autotransformer; one end of the other AC port is connected to the main winding of the multi-winding autotransformer, and the other end of the other AC port is connected to the feeder to form a series configuration between two feeders.

3. The flexible interconnection device according to claim 2, wherein The number of auxiliary windings of the multi-winding autotransformer is jointly determined by the number of connected feeders and the number of cascade units.

4. The flexible interconnection device according to any one of claims 1-3, characterized in that Each of the cascade units includes a plurality of cascade sub-modules for realizing different functions; each of the cascade sub-modules includes two AC ports; one of the AC ports is connected to an auxiliary winding of the transformer to become an input port; the other AC port is cascaded with other cascade sub-modules in the same cascade unit and then connected in series with the line to form a regulated voltage and become an output port; One end of the output port is connected to the output port of the upper-level cascade unit or connected to the main winding of the transformer, and the other end of the output port is connected to the output port of the lower-level cascade unit or connected to the feeder to form a series configuration between two feeders for outputting a series compensation voltage to continuously adjust the line power flow.

5. The flexible interconnection device according to claim 4, characterized in that, The cascade sub-module adopts any one of the following forms: - The cascade sub-module adopts a full-bridge form, wherein the input port of the full-bridge form is connected to an auxiliary winding or the first winding of the transformer as a balance port for maintaining the stability of the internal energy of the cascade sub-module and adjusting the amplitude and phase of the series voltage; - The cascade sub-module adopts a thyristor type step voltage regulator form, and the input port of the thyristor type step voltage regulator form is connected to an auxiliary winding or the first winding of the transformer for adjusting the amplitude of the series voltage.

6. The flexible interconnection device according to claim 1, wherein Also comprising: Selecting one feeder as an active power balance feeder; The active power of the balance feeder is automatically balanced according to the distribution of the line active power.

7. A multi-functional integrated movable multi-port flexible interconnection device, characterized in that, Comprising the flexible interconnection device according to any one of claims 1-6, and a plurality of AC ports, a plurality of DC ports and an access port for connecting an emergency power supply device and an energy storage device provided on the flexible interconnection device; wherein: Each of the AC ports has a different voltage level, and all the AC ports are subjected to power flow decoupling control through the flexible interconnection device; Each of the DC ports has a different voltage level, and all the DC ports are subjected to voltage control through the flexible interconnection device.

8. The multifunctional integrated movable multi-port flexible interconnection device according to claim 7, characterized in that, It further includes any one or more of the following: - A reactive power compensation device disposed inside the flexible interconnection device; the reactive power compensation device is connected to an auxiliary winding of a transformer in the flexible interconnection device and is used for reactive power control of the balanced feeder; - An AC-AC converter disposed inside the flexible interconnection device; one end of the AC-AC converter is connected to an auxiliary winding of a transformer in the flexible interconnection device; the other end of the AC-AC converter is connected to an AC power source and is used for joint power supply of multiple feeders in an emergency scenario; - An AC-DC converter disposed inside the flexible interconnection device; the AC port of the AC-DC converter is connected to an auxiliary winding of a transformer in the flexible interconnection device; the DC port of the AC-DC converter is connected to a DC microgrid and is used for realizing the application of optical storage and DC flexibility; or The DC port of the AC-DC converter is connected to a solar photovoltaic or energy storage device and is used for directly absorbing new energy power.

9. A control method for a multi-functional integrated movable multi-port flexible interconnection device, characterized in that, When the transformer of the flexible interconnection device adopts a multi-winding autotransformer and the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, for realizing the internal energy balance of the multifunctional integrated mobile multi-port flexible interconnection device, it includes: Expressing the internal energy balance of the multifunctional integrated mobile multi-port flexible interconnection device as the capacitor voltage of the DC bus remaining stable, it is required that the active power flowing into the capacitor of the DC bus remains zero; by adjusting the voltage of the balance port and the magnitude and size of the differential mode current, which is the difference between the currents at the two taps of the auxiliary winding, the internal energy balance of the multi-winding autotransformer is achieved.

10. A control method for a multifunctional integrated movable multi-port flexible interconnection device, characterized in that, When the cascaded sub-module of the power electronic converter of the flexible interconnection device adopts a full-bridge form, for realizing the reactive power compensation of the balanced feeder of the multifunctional integrated mobile multi-port flexible interconnection device, it includes: According to the magnetic potential balance of the transformer, when the primary winding of the transformer is connected to the power source, a magnetic flux will be generated in the magnetic circuit, and induced electromotive forces will be induced in the primary and secondary windings to balance the power source voltage. When the change in the power source voltage is less than the set threshold, the magnetic flux in the magnetic circuit remains unchanged; after the load is connected, a current flows through the secondary winding, which will also generate a magnetic potential and affect the magnetic flux in the magnetic circuit, thereby affecting the values of the induced electromotive forces in the primary and secondary windings; when the magnetic flux in the magnetic circuit changes, since the power source voltage remains unchanged, the current in the primary winding will automatically change to keep the magnetic flux in the magnetic circuit unchanged, and the change in the magnetic potential in the magnetic circuit caused by the change in the primary winding current basically compensates for the influence of the change in the load on the magnetic flux in the magnetic circuit due to the change in the secondary winding; at this time, the change in the current in the secondary winding affects the current in the line at the head end of the transformer; According to the relationship between the differential-mode current and the current at the head end of the line, the reactive power at the head end is controlled by controlling the differential-mode current; since the energy balance and the reactive power of the balanced feeder are both controlled by the full-bridge cascaded sub-module, at this time, on the premise of ensuring the energy balance of the flexible interconnection device, a reactive power compensation device is connected to other auxiliary windings to achieve the decoupled control of the power flow of all feeders.

11. The control method of the multifunctional integrated movable multi-port flexible interconnection device according to claim 9 or 10, characterized in that The control system of the power electronic converter includes: A detection circuit for detecting the system variables required by the control system and the variable values of the reactive power compensator. Among them, the detection objects include: grid voltage, power factor, active and reactive components of the grid current, and active and reactive components of the current of the compensation device; A control circuit for analyzing and processing the detected signals, calculating the active and reactive power factors by sampling the voltage and current signals of the system, and determining relevant control parameters according to the reference values set by the system; A trigger circuit for generating trigger pulses required for the thyristor trigger angle. The trigger circuit includes a synchronous conversion circuit for processing the grid AC signal and an isolation and amplification circuit for pulse signals.

12. An emergency power supply vehicle, characterized in that, Adopt the multifunctional integrated movable multi-port flexible interconnection device described in claim 8 or 9, and connect the multifunctional integrated movable multi-port flexible interconnection device to the emergency power supply device through the emergency power supply device access port for realizing the combined power supply of multiple feeders in an emergency scenario.

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