Modular flexible interconnect device and system

Abstract

The application discloses a combined flexible interconnection device and system. The combined flexible interconnection device comprises a series compensation module, a parallel compensation module, a flexible interconnection module and a thyristor switch. The series compensation module comprises an AC input port and an AC output port. The AC input port is connected with an AC power grid and serves as an AC input port of the combined flexible interconnection device. The AC output port is connected with the thyristor switch. The parallel compensation module comprises a first AC port and a first DC port. The first AC port adopts a three-wire four-line system and is connected between the AC output port and an AC load. The first DC port is connected with a stabilizing capacitor. The flexible interconnection module comprises a second AC port and a second DC port. The second AC port adopts a three-wire four-line system and is connected between the thyristor switch and the parallel compensation module. The second DC port serves as a DC interconnection port of the combined flexible interconnection device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-voltage AC-DC hybrid power distribution, in particular to a combined flexible interconnection device and system. BACKGROUND

[0002] With the continuous development of social demand and power grid technology, the vigorous promotion of distributed energy, the rapid growth of load and the diversification of access have changed the structure and operation characteristics of the traditional distribution network. The specific performance is as follows: the power supply capacity is insufficient, the load fluctuates sharply, the voltage fluctuates, the power quality is difficult to guarantee, the power supply reliability is low, the active power and reactive power flow direction is complex, the short-circuit current is difficult to predict and other problems.

[0003] The flexible interconnection device is an AC-DC hybrid distribution network equipment based on power electronic technology, which can enhance the controllable ability of the distribution network, further improve the power regulation, voltage / reactive power comprehensive control, power quality comprehensive management and safety and operation reliability of the distribution system, and enhance the active regulation and the ability to accept multiple types of distributed power and load of the distribution network. The existing technology cannot realize flexible power interconnection of distribution area, comprehensive management of system side and load side power quality, DC short circuit protection and short circuit point positioning.

[0004] In view of the technical problems in the prior art that the existing technology cannot realize flexible power interconnection of distribution area, comprehensive management of system side and load side power quality, DC short circuit protection and short circuit point positioning, no effective solution has been proposed so far. SUMMARY

[0005] The present disclosure provides a combined flexible interconnection device and system to at least solve the technical problems in the prior art that the existing technology cannot realize flexible power interconnection of distribution area, comprehensive management of system side and load side power quality, DC short circuit protection and short circuit point positioning.

[0006] According to one aspect of the present application, a combined flexible interconnection device is provided, comprising: a series compensation module, a parallel compensation module, a flexible interconnection module, and a thyristor switch, wherein the series compensation module comprises an AC input port and an AC output port, the AC input port is connected with an AC power grid as an AC input port of the combined flexible interconnection device, and the AC output port is connected with the thyristor switch; the parallel compensation module comprises a first AC port and a first DC port, the first AC port is connected between the AC output port and an AC load in a three-phase four-wire system, and the first DC port is connected with a stabilizing capacitor; the flexible interconnection module comprises a second AC port and a second DC port, wherein the second AC port is connected from the middle of the thyristor switch and the parallel compensation module in a three-phase four-wire system, and the second DC port is a DC interconnection port of the combined flexible interconnection device, used to realize connection with a DC side of another combined flexible interconnection device.

[0007] Optionally, the series compensation module further comprises: a first AC / DC converter, a first single-phase transformer, a second single-phase transformer, and a third single-phase transformer, wherein the first AC / DC converter comprises an AC / DC converter and a first DC / AC converter, the AC / DC converter and the first DC / AC converter are connected back-to-back, the AC side of the AC / DC converter is connected with A, B, C, and N terminals of the AC input port, the AC side A1, A2, and A3 terminals of the first DC / AC converter are respectively connected with the primary side of the first single-phase transformer, the second single-phase transformer, and the third single-phase transformer, and the AC side N terminal of the first DC / AC converter is connected with the N terminal of the AC input port.

[0008] The other end of the source side of the first single-phase transformer, the second single-phase transformer, and the third single-phase transformer is connected with the N terminal of the AC input port, and the secondary side is connected in series between the AC input port and the AC output port.

[0009] Optionally, the parallel compensation module comprises: an LCL filter, a second converter module, and a stabilizing capacitor, wherein

[0010] One end of the LCL filter is connected with the AC input port;

[0011] The second converter module adopts a three-phase four-bridge arm topology, one end of which is connected with the LCL filter, and the other end is connected with the stabilizing capacitor through the first DC port.

[0012] Optionally, the flexible interconnection module further comprises: a second DC / AC converter, a DC / DC converter, and a DC stabilizing capacitor, wherein

[0013] The second DC / AC converter is connected to the thyristor switch at one end and to the AC load at the other end, and comprises a DC / AC LC filter and a DC / AC converter module, wherein the DC / AC converter module is a three-phase three-bridge topology.

[0014] The DC / DC converter high-voltage DC side and the second DC / AC converter high-voltage DC side share a DC voltage stabilizing capacitor, the low-voltage DC side is used as a DC interconnection port, and comprises a DC / DC LC filter and a DC / DC converter module, wherein the DC / DC converter module is a half-bridge topology.

[0015] Optionally, the thyristor switches CR1, CR2 and CR3 are connected to the A, B and C three-phase of the AC input port respectively, and adopt an anti-parallel thyristor structure.

[0016] Optionally, the second DC / AC converter comprises a constant DC voltage mode and a constant AC V / f control mode, and the DC / DC converter comprises three control modes: a constant high-voltage voltage mode, a constant low-voltage voltage mode, wherein

[0017] When the AC power supply is normal, the second DC / AC converter adopts the constant DC voltage control mode, and the DC / DC converter adopts the constant low-voltage voltage mode;

[0018] When the AC power supply is lost, the thyristor switch is turned off, the DC / DC converter adopts the constant high-voltage voltage mode, and the second DC / AC converter adopts the constant AC V / f control mode.

[0019] According to another aspect of the present application, a combined flexible interconnection device is provided, comprising at least two of any of the above-mentioned combined flexible interconnection devices.

[0020] Therefore, the combined flexible interconnection device and system provided by the embodiment realizes the access and coordinated control of low-voltage AC / DC hybrid distribution network DC load or distributed energy, the power mutual assistance function of two districts through the DC side flexible interconnection, the comprehensive power quality management of the distribution network, the support of important load, the DC short-circuit protection and short-circuit point positioning function, and has a simple structure and reliable operation. Further, the technical problems that the prior art cannot realize the flexible power mutual assistance of the distribution district, the comprehensive management of the system side and the load side power quality, the DC short-circuit protection and the short-circuit point positioning are solved.

[0021] The above and other objects, advantages and features of the present application will become more apparent from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Some specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. The same reference signs in the drawings denote the same or similar components or parts. Those skilled in the art should understand that the drawings are not necessarily drawn to scale. In the drawings:

[0023] Figure 1 is a schematic diagram of a combined flexible interconnection device according to a first aspect of embodiments of the present application;

[0024] Figure 2 is a schematic diagram of a series compensation module according to the first aspect of embodiments of the present application;

[0025] Figure 3 is a schematic diagram of a parallel compensation module according to the first aspect of embodiments of the present application;

[0026] Figure 4 is a schematic diagram of a flexible interconnection module and the thyristor switch according to the first aspect of embodiments of the present application;

[0027] Figure 5 is a schematic diagram of a combined flexible interconnection system according to a second aspect of embodiments of the present application.

[0028] The series compensation module 10, the parallel compensation module 20, the flexible interconnection module 30, the thyristor switch 40, the AC input port 11, the AC output port 12, the first AC port 21, the first DC port 22, the second AC port 31, the second DC port 32, the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments and features in the present disclosure can be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0030] In order to enable persons skilled in the art to better understand the present disclosure scheme, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below in combination with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, not all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present disclosure.

[0031] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present disclosure and above-described drawings are used to distinguish between similar objects and not necessarily for describing a specific sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the present disclosure described herein are capable of operation in other sequences than illustrated or otherwise described herein. Moreover, the terms "comprise", "have" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, article, or apparatus that comprises a list of steps or units can not necessarily be limited to those steps or units, but can include additional steps or units not expressly listed or inherent to such process, method, article, or apparatus.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0033] Figure 1 is a schematic diagram of a combined flexible interconnection device according to a first aspect of embodiments of the present application; Figure 2 is a schematic diagram of a series compensation module according to the first aspect of embodiments of the present application; Figure 3 is a schematic diagram of a shunt compensation module according to the first aspect of embodiments of the present application;

[0034] Figure 4 is a schematic diagram of a flexible interconnection module and a thyristor switch according to the first aspect of embodiments of the present application. Referring to Figures 1 to 4 the combined flexible interconnection device comprises a series compensation module, a shunt compensation module, a flexible interconnection module and a thyristor switch, wherein

[0035] the series compensation module comprises an AC input port and an AC output port, the AC input port is connected with an AC power grid as an AC input port of the combined flexible interconnection device, and the AC output port is connected with the thyristor switch;

[0036] the shunt compensation module comprises a first AC port and a first DC port, the first AC port is connected between the AC output port and an AC load in a three-phase four-wire system, and the first DC port is connected with a stabilizing capacitor;

[0037] The flexible interconnection module comprises a first alternating current port and a second direct current port, wherein the first alternating current port adopts three-phase four-wire system, is connected from the middle of the thyristor switch and the parallel compensation module, and the second direct current port is a direct current interconnection port of the combined flexible interconnection device, and is used for realizing connection with a direct current side of another combined flexible interconnection device.

[0038] Specifically, referring to FIG. 1, Figures 1 to 4 The series compensation module is a two-port module and adopts three-phase four-wire system. The series compensation module has two alternating current ports, an alternating current input port connected to an alternating current power grid and serving as an alternating current input port of the entire combined flexible interconnection device. The alternating current output port is connected to the thyristor switch. When the alternating current power grid voltage fluctuates, the series compensation module ensures the alternating current output port voltage to be stable through compensation, and can reduce the regulation frequency of the on-load tap changer of the upper power grid.

[0039] The flexible interconnection module is a two-port module. One is a second alternating current port, which adopts three-phase four-wire system; the other is a second direct current port, which realizes interconnection with other distribution networks and access of distributed power. The alternating current port is connected from the middle position of the thyristor switch and the parallel compensation module. The direct current port serves as a direct current interconnection port of the entire combined flexible interconnection device, realizes connection with a direct current side of another combined flexible interconnection device of a station area, and also serves as an access port of direct current distributed power and loads such as an energy storage system, a photovoltaic system, a direct current load and an electric vehicle charging pile. The flexible interconnection module can realize functions of setting the direct current side bus voltage and setting the power when connected to the power grid, realize functions of setting the alternating current V / f control when off-grid, and realize functions of short-circuit protection and setting the short-circuit current control when a short circuit occurs. The access and coordinated control of the direct current load or distributed power can be realized through the establishment of the direct current bus voltage; the power interconnection function of two station areas through the direct current side flexible interconnection can be realized through the setting power control; the important load support can be realized through the setting alternating current V / f control; and the direct current short-circuit protection and short-circuit point positioning function can be realized through the setting short-circuit current function.

[0040] The access of the thyristor switch can ensure the quick conversion of the flexible interconnection module between the on-grid mode and the off-grid mode, so as to realize seamless voltage support of important loads. In the single-machine mode, that is, when the direct current interconnection port has the energy storage system access but is not interconnected with another station area, when the station area power grid loses power, the flexible interconnection module automatically converts to the off-grid V / f mode, so as to ensure that the important load does not lose power. In the interconnection mode, the power interconnection function is realized through the direct current interconnection port with another station area, and at the same time, when the alternating current power grid of one station area loses power, the important load of the power-losing station area can be powered by the combined flexible interconnection device of the non-power-losing station area through the direct current interconnection port.

[0041] When a short circuit occurs in the DC bus connected to the DC interconnection port, the flexible interconnection module can cut off the short circuit current in microseconds to realize the short circuit protection function. After detecting the short circuit state, the flexible interconnection module can issue a current setting instruction, and at this time, the current will completely flow into the short circuit point, and when there are many DC side devices, the short circuit point positioning function can be quickly realized.

[0042] The parallel compensation module is an AC port module and adopts a three-phase four-wire system. The AC port is connected between the AC output port of the flexible interconnection module and the important load. When the load has non-linear, reactive, unbalanced load and other conditions, the parallel compensation module realizes the three-phase balanced, harmonic-free and unity power factor of the AC grid side current waveform through harmonic compensation, reactive compensation and unbalanced compensation functions.

[0043] Thus, through the decoupling control of the series compensation module, the parallel compensation module and the flexible interconnection module, the low-voltage AC / DC hybrid distribution network realizes the access and coordinated control of DC loads or distributed energy, the power mutual aid function of two districts through the DC side flexible interconnection, the comprehensive power quality management of the distribution network, the support of important loads, the DC short circuit protection and the short circuit point positioning function, and has a simple structure and reliable operation. Further, the technical problems that the existing technology cannot realize flexible power mutual aid of the distribution district, comprehensive system side and load side power quality management, DC short circuit protection and short circuit point positioning are solved.

[0044] Optionally, the series compensation module further comprises a first AC module, a first single-phase transformer, a second single-phase transformer and a third single-phase transformer, wherein

[0045] The first AC module comprises an AC / DC converter and a first DC / AC converter, wherein the AC / DC converter and the first DC / AC converter are connected back-to-back, the AC side of the AC / DC converter is connected with the A, B, C and N terminals of the AC input port, the AC side A1, A2 and A3 terminals of the first DC / AC converter are respectively connected with the primary sides of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer, and the AC side N terminal of the first DC / AC converter is connected with the N terminal of the AC input port.

[0046] The other end of the source end of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer is connected with the N terminal of the AC input port, and the secondary sides are connected in series between the AC input port and the AC output port.

[0047] Specifically, reference is made to Figure 2As shown, the series compensation module includes a first converter module, three single-phase transformers T1 / T2 / T2. Among them, the converter module is connected back-to-back by the DC side of the AC / DC converter and the first DC / AC converter, the AC side of the AC / DC converter is connected to the AC input port A / B / C / N, the AC side A1 / B1 / C1 of the first DC / AC converter is connected to the primary side of the three single-phase transformers T1 / T2 / T3 respectively, the AC side N of the converter is connected to the input port N, and the other end of the primary side of the three single-phase transformers is connected to the AC input port N. The secondary sides of the three single-phase transformers are connected in series between the AC input port and the AC output port. Among them, the AC / DC converter adopts constant DC voltage control, and the first DC / AC converter adjusts its output voltage to form an AC output compensation voltage according to the voltage regulation instruction and the actual AC input voltage waveform, and then realizes series voltage compensation through T1 / T2 / T3 transformers to complete the voltage quality management function of the AC output port.

[0048] Optionally, the parallel compensation module includes: an LCL filter, a second converter module, and a stabilizing capacitor, wherein

[0049] One end of the LCL filter is connected to the AC input port;

[0050] The second converter module adopts a three-phase four-bridge arm topology, one end of which is connected to the LCL filter, and the other end is connected to the stabilizing capacitor through the first DC port.

[0051] Specifically, the first AC port of the parallel compensation module is connected between the AC power grid and the AC load, and is connected in parallel with the AC load, and the first DC port is connected to the voltage stabilizing capacitor. The parallel compensation module mainly consists of an LCL filter, a second converter module, a voltage stabilizing capacitor and the like. The second converter module adopts a three-phase four-bridge arm topology. When the AC load contains unbalanced / reactive / non-linear components, the unbalanced compensation / reactive compensation / harmonic compensation function of the parallel compensation module is used to make the AC power grid side balanced / harmonic-free / unit power factor current. The series compensation module and the parallel compensation module can realize the comprehensive power quality management function of the AC input port and the AC output port.

[0052] Optionally, the flexible interconnection module further includes: a second DC / AC converter, a DC / DC converter, and a DC voltage stabilizing capacitor, wherein

[0053] One end of the AC side of the second DC / AC converter is connected to a thyristor switch, the other end is connected to an AC load, and includes a DC / AC LC filter and a DC / AC converter module, wherein the DC / AC converter module is a three-phase three-bridge arm topology;

[0054] The DC / DC converter high-voltage DC side and the second DC / AC converter high-voltage DC side share a DC voltage stabilizing capacitor, the low-voltage DC side serves as a DC interconnection port, and the DC / DC converter module is a half-bridge topology.

[0055] Optionally, the thyristor switches CR1, CR2 and CR3 are connected to the A, B and C three-phase of the AC input port respectively, and adopt an anti-parallel thyristor structure.

[0056] Specifically, as shown in the figure, Figure 4 Specifically, as shown in the figure,

[0057] Optionally, the second DC / AC converter includes a constant DC voltage mode and a constant AC V / f control mode, and the DC / DC converter includes three control modes: a constant high-voltage mode and a constant low-voltage mode.

[0058] When the AC power grid is normally powered, the second DC / AC converter adopts a constant DC voltage control mode, and the DC / DC converter adopts a constant low-voltage mode.

[0059] When the AC power grid loses power, the thyristor switch is turned off, the DC / DC converter adopts a constant high-voltage mode, and the second DC / AC converter adopts a constant AC V / f control mode.

[0060] Specifically, the DC / AC converter of the flexible interconnection module has three control modes: constant power control, constant DC voltage and constant AC V / f control, and the DC / DC converter has three control modes: constant high-voltage, constant low-voltage and constant power control.

[0061] The mechanism for realizing important load support is as follows: when the AC power grid is normally powered, the DC / AC converter operates in a constant DC voltage control mode, and the DC / DC converter operates in a constant low-voltage mode. When the AC power grid loses power, the control thyristor switch is turned off, and the operating mode of the DC / DC converter is switched to a constant high-voltage mode, and the DC / AC converter is switched to a constant V / f control mode. This conversion process is completed within 10 milliseconds, and the AC important load support function can be realized.

[0062] The short-circuit detection process of the flexible interconnection module is as follows: when a short circuit occurs on the DC side of the combined flexible interconnection device during grid-connected operation, the DC / DC converter first detects the fault and protects, and the internal IGBT switch is quickly turned off to realize the short-circuit protection function. Subsequently, after the DC / DC converter fails to recover, it is switched to a standby state, and a set current is output from the low-voltage port of the DC / DC converter according to the current set value, which will completely flow into the short-circuit point, and the short-circuit detection function is completed by sampling the current of each port on the DC side.

[0063] In addition, Figure 5 A combined flexible interconnection device is shown in the second aspect of the embodiments of the present application, and the first aspect of the embodiments of the present application is described with reference to Figures 1-5 As shown in the second aspect of the embodiments of the present application, the combined flexible interconnection device comprises at least two combined flexible interconnection devices according to any one of the first aspect of the embodiments of the present application.

[0064] Specifically, the two areas are connected through the DC interconnection port of the combined flexible interconnection device to realize flexible interconnection between the two areas. The DC port can still be connected to a storage system, a photovoltaic system, a DC load, an electric vehicle charging pile, and other DC devices.

[0065] As shown in the second aspect of the embodiments of the present application, Figure 5 As shown in the second aspect of the embodiments of the present application, the process of realizing bidirectional power regulation between areas, areas and photovoltaic systems, and storage systems by the flexible interconnection module is as follows: when the flexible interconnection module is in a grid-connected mode, the flexible interconnection module 1 can operate in a constant DC voltage mode, and the flexible interconnection module 2 can operate in a constant power mode. By adjusting the power set value of the flexible interconnection module 2, the power interconnection and regulation between areas can be realized.

[0066] As shown in the second aspect of the embodiments of the present application, Figure 5 As shown in the second aspect of the embodiments of the present application, if there is no distributed power source such as a photovoltaic system or a storage system connected to the DC interconnection side and only a DC load, when the area 1 loses power, the process of realizing important load support is as follows: if the area 1 loses power, the combined flexible interconnection device 1 automatically switches to an off-grid mode, and the flexible interconnection module 1 is switched from a constant DC voltage mode to a constant V / f mode. Through communication between the combined flexible interconnection devices of the two areas, the flexible interconnection module 2 is switched to a constant DC voltage mode, thereby ensuring that the AC side load of the area 1 and the area 2 does not lose power.

[0067] The low-voltage AC-DC hybrid distribution network realizes the access and coordinated control of DC load or distributed energy through the flexible interconnection module, realizes the power mutual aid function through the DC side flexible interconnection between two districts, realizes the comprehensive power quality treatment of the distribution network, supports important load, realizes the DC short-circuit protection and short-circuit point positioning function.

[0068] In addition, the combined flexible interconnection system in the second aspect of the embodiments of the present application refers to the content of the first aspect of the embodiments of the present application, which will not be repeated here.

[0069] Therefore, the combined flexible interconnection device and system provided by the embodiments realize the access and coordinated control of DC load or distributed energy of the low-voltage AC-DC hybrid distribution network, realize the power mutual aid function through the DC side flexible interconnection between two districts, realize the comprehensive power quality treatment of the distribution network, support important load, realize the DC short-circuit protection and short-circuit point positioning function through the decoupling control of the series compensation module, the parallel compensation module and the flexible interconnection module, and have simple structure and reliable operation. Further, the technical problems that the existing technology cannot realize the flexible power mutual aid of the distribution district, the comprehensive treatment of the system side and the load side power quality, the DC short-circuit protection and the short-circuit point positioning are solved.

[0070] Unless specifically stated otherwise, the relative arrangements of the components and steps, numerical expressions, and values set forth in the examples herein are not intended to limit the scope of the present disclosure. It will be understood that the dimensions of the various parts shown in the drawings are not necessarily to scale, and that for purposes of convenience and clarity in understanding the present disclosure, common terms have not been specifically defined prior to their use. Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail but can be assumed known to the person of ordinary skill in the art. In the examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as a limitation on the scope of the exemplary embodiments. Thus, other examples of the exemplary embodiments can have different values. It should be noted that like reference numerals and letters refer to like items in the several views of the drawings, and thus, once an item is defined in one view, it need not be discussed further in subsequent views.

[0071] For purposes of the description hereinafter, spatial or directional terms, such as, for example, "above", "below", "upper", "lower", "horizontal", "vertical", "top", "bottom", and the like, relative to the orientation of the device as shown in the drawings, are used. It is to be understood that the spatial and directional terms are used for purposes of the description and illustration and that the device can assume various orientations, except where the context of use dictates otherwise. For example, the device can be inverted, rotated 90 degrees or otherwise positioned, and the spatial and directional terms used herein are to be interpreted accordingly.

[0072] In the description of the present disclosure, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the present disclosure and simplifying the description, these orientation words do not indicate and imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the protection scope of the present disclosure; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0073] The above description is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A combined flexible interconnection device for enabling flexible interconnection between different distribution zones, characterized in that, The application relates to a combined flexible interconnection device, which comprises a series compensation module, a parallel compensation module, a flexible interconnection module and a thyristor switch, wherein the series compensation module comprises an AC input port and an AC output port, the AC input port is connected with an AC power grid as an AC input port of the combined flexible interconnection device, and the AC output port is connected with the thyristor switch; the parallel compensation module comprises a first AC port and a first DC port, the first AC port is connected between the AC output port and an AC load in a three-phase four-wire system, and the first DC port is connected with a stabilizing capacitor; the flexible interconnection module comprises a second AC port and a second DC port, wherein the second AC port is connected between the thyristor switch and the parallel compensation module in a three-phase four-wire system, and the second DC port is a DC interconnection port of the combined flexible interconnection device and is used for realizing connection with a DC side of other combined flexible interconnection devices; the series compensation module further comprises a first AC module, a first single-phase transformer, a second single-phase transformer and a third single-phase transformer, wherein the first AC module comprises an AC / DC converter and a first DC / AC converter, wherein the AC / DC converter and the first DC / AC converter are connected back to back, the AC side of the AC / DC converter is connected with A, B, C and N terminals of the AC input port, the AC side A1, A2 and A3 terminals of the first DC / AC converter are respectively connected with primary sides of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer, and the AC side N terminal of the first DC / AC converter is connected with the N terminal of the AC input port; the other end of the source end of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer is connected with the N terminal of the AC input port, and the secondary sides are connected in series between the AC input port and the AC output port; the parallel compensation module comprises an LCL filter, a second converter module and the stabilizing capacitor, wherein one end of the LCL filter is connected with the AC input port; the second converter module adopts a three-phase four-bridge arm topology, one end of the second converter module is connected with the LCL filter, and the other end of the second converter module is connected with the stabilizing capacitor through the first DC port. the flexible interconnection module further comprises a second DC / AC converter, a DC / DC converter and a DC voltage stabilizing capacitor, wherein 2. The modular flexible interconnection device of claim 1, wherein, one end of the AC side of the second DC / AC converter is connected with the thyristor switch, and the other end of the AC side of the second DC / AC converter is connected with the AC load, and the second DC / AC converter comprises a DC / AC LC filter and a DC / AC converter module, wherein the DC / AC converter module is a three-phase three-bridge arm topology; the high-voltage DC side of the DC / DC converter and the high-voltage DC side of the second DC / AC converter share the DC voltage stabilizing capacitor, the low-voltage DC side is used as the DC interconnection port, and the DC / DC converter comprises a DC / DC LC filter and a DC / DC converter module, wherein the DC / DC converter module is a half-bridge topology. ​ 3. The modular flexible interconnection device of claim 1, wherein, The thyristor switches CR1, CR2 and CR3 are connected to the A, B and C phases of the AC input port respectively and adopt an anti-parallel thyristor structure.

4. The modular flexible interconnection device of claim 2, wherein, The second DC / AC converter comprises a constant DC voltage mode and a constant AC V / f control mode, and the DC / DC converter comprises three control modes: a constant high voltage mode and a constant low voltage mode. When the AC power supply is normal, the second DC / AC converter adopts the constant DC voltage control mode, and the DC / DC converter adopts the constant low voltage mode. When the AC power supply is lost, the thyristor switches are turned off, the DC / DC converter adopts the constant high voltage mode, and the second DC / AC converter adopts the constant AC V / f control mode.

5. A combined flexible interconnection system, characterized in that The combined flexible interconnection device comprises a series compensation module, a parallel compensation module, a flexible interconnection module and a thyristor switch. The series compensation module comprises an AC input port and an AC output port, the AC input port is connected to an AC power grid and serves as an AC input port of the combined flexible interconnection device, and the AC output port is connected to the thyristor switch. The parallel compensation module comprises a first AC port and a first DC port, the first AC port adopts a three-phase four-wire system, is connected between the AC output port and an AC load, and the first DC port is connected to a stabilizing capacitor. The flexible interconnection module comprises a first AC port and a second DC port, the first AC port adopts a three-phase four-wire system, is connected between the thyristor switch and the parallel compensation module, and the second DC port is a DC interconnection port of the combined flexible interconnection device and is used to realize DC side connection with other combined flexible interconnection devices.

6. The combined flexible interconnection system according to claim 5, characterized in that The series compensation module further comprises a first AC module, a first single-phase transformer, a second single-phase transformer and a third single-phase transformer. The first AC module comprises an AC / DC converter and a first DC / AC converter, the AC / DC converter and the first DC / AC converter are connected back-to-back, the AC side of the AC / DC converter is connected to the A, B, C and N terminals of the AC input port, the AC side A1, A2 and A3 terminals of the first DC / AC converter are connected to the primary sides of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer respectively, and the AC side N terminal of the first DC / AC converter is connected to the N terminal of the AC input port. The other ends of the source terminals of the first single-phase transformer, the second single-phase transformer and the third single-phase transformer are connected to the N terminal of the AC input port, and the secondary sides thereof are connected in series between the AC input port and the AC output port.

7. The combined flexible interconnection system of claim 5, wherein, The parallel compensation module comprises an LCL filter, a second converter module and the stabilizing capacitor. One end of the LCL filter is connected to the AC input port. The second converter module adopts a three-phase four-bridge-arm topology, one end of which is connected with the LCL filter, and the other end is connected with the stable capacitor through the first DC port.

8. The combined flexible interconnection system of claim 5, wherein, The flexible interconnection module further comprises a second DC / AC converter, a DC / DC converter and a DC stable capacitor, wherein The second DC / AC converter is connected with the thyristor switch at one end and connected with the AC load at the other end, and comprises a DC / AC LC filter and a DC / AC converter module, wherein the DC / AC converter module adopts a three-phase three-bridge-arm topology. The DC / DC converter high-voltage DC side and the second DC / AC converter high-voltage DC side share the DC stable capacitor, the low-voltage DC side is used as the DC interconnection port, and comprises a DC / DC LC filter and a DC / DC converter module, wherein the DC / DC converter module adopts a half-bridge topology.

9. The combined flexible interconnection system of claim 5, wherein, The thyristor switches CR1, CR2 and CR3 are connected to the A, B and C three-phase of the AC input port respectively, and adopt an anti-parallel thyristor structure.

10. The combined flexible interconnection system of claim 8, wherein, The second DC / AC converter comprises a constant DC voltage mode and a constant AC V / f control mode, and the DC / DC converter comprises three control modes: a constant high-voltage mode and a constant low-voltage mode, wherein When the AC power grid is normally powered, the second DC / AC converter adopts the constant DC voltage control mode, and the DC / DC converter adopts the constant low-voltage mode; When the AC power grid loses power, the thyristor switch is turned off, the DC / DC converter adopts the constant high-voltage mode, and the second DC / AC converter adopts the constant AC V / f control mode.

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