Cross-voltage multi-port power distribution network flexible interconnection system and control method thereof

Abstract

The invention relates to a cross-voltage multi-port power distribution network flexible interconnection system and a control method thereof.The cross-voltage multi-port power distribution network flexible interconnection system comprises a medium-voltage voltage source converter, a direct current conversion assembly and a flexible interconnection assembly, and the medium-voltage voltage source converter is used for converting first alternating current output by a first alternating current power grid into first direct current; the direct current conversion assembly is used for setting a concentrated medium-voltage direct current bus based on the first direct current or converting the first direct current into second direct current and setting a concentrated low-voltage direct current bus based on the second direct current, and the voltage of the first direct current is higher than that of the second direct current; the first side of the flexible interconnection assembly is connected with the concentrated low-voltage direct-current bus or the concentrated medium-voltage direct-current bus, and the second side and the third side of the flexible interconnection assembly are connected with the alternating-current system corresponding to the flexible interconnection assembly. Therefore, the problems of insufficient transmission capacity and operation flexibility and the like of the medium-voltage and low-voltage power supply areas are solved, and the flexibility and the planning operation economy of the medium-voltage and low-voltage power supply areas are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a cross-voltage multi-port distribution network flexible interconnection system and a control method thereof. Background Art

[0002] In order to make the distribution network more effectively adapt to the multi-form and large-scale access of new "source-load-storage" such as distributed power sources, car charging piles, and energy storage, the flexible interconnection system of the distribution network based on power electronic equipment has become a research hotspot in the field of distribution network because it has the advantages of changing the distribution network with traditional closed-loop design and open-loop operation to flexible closed-loop operation, real-time optimization of line flow distribution, and realization of real-time fine power control at the feeder level. The networking mode of the flexible interconnection system of the distribution network is closely related to its technical effect and economic benefits. Unreasonable networking forms will not only make it difficult to effectively improve the flexibility and reliability of the distribution network, but will also increase the construction cost.

[0003] However, the single-level flexible interconnection method usually adopted by related technologies is unable to fully consider the complementary characteristics of medium and low voltage power supply areas in transmission capacity and operational flexibility in the face of the multi-form, multi-level, and multi-voltage level large-scale access of new "source-load-storage" in the distribution network. There is still much room for improvement in flexibility and planning and operating economy, which needs to be urgently addressed. Summary of the invention

[0004] The present invention provides a cross-voltage multi-port distribution network flexible interconnection system and a control method thereof to solve the problems of insufficient transmission capacity and operation flexibility in medium and low voltage power supply areas, and to improve the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0005] A first aspect of the present invention provides a cross-voltage multi-port distribution network flexible interconnection system, comprising: a medium voltage voltage source converter, a DC conversion component and a flexible interconnection component, wherein the medium voltage voltage source converter is used to convert a first alternating current output by a first AC power grid into a first direct current; the DC conversion component is used to set up a centralized medium voltage DC bus based on the first direct current, or to convert the first direct current into a second direct current, and to set up a centralized low voltage DC bus based on the second direct current, wherein the voltage of the first direct current is higher than the voltage of the second direct current; the first side of the flexible interconnection component is connected to the centralized low voltage DC bus or the centralized medium voltage DC bus, and the second side and the third side of the flexible interconnection component are both connected to the AC system corresponding to the flexible interconnection component, and are used to convert the first direct current into a second alternating current, or to convert the second direct current into a third alternating current.

[0006] Furthermore, in some embodiments, when the distance between each interconnected system is within a first preset distance interval, the DC conversion component includes: a medium voltage-low voltage DC transformer, used to convert the first DC power into the second DC power; and a first setting unit, used to set the centralized low voltage DC bus based on the second DC power.

[0007] Among them, the medium-voltage-low-voltage DC transformer is the key equipment to realize the conversion of medium-voltage DC power to low-voltage DC power. It can convert the higher medium-voltage DC voltage into a low-voltage DC voltage suitable for electrical equipment to meet the needs of different voltage levels. It has high efficiency in the power conversion process, can reduce energy loss and improve energy utilization efficiency.

[0008] Furthermore, in some embodiments, the medium voltage-low voltage DC transformer adopts at least one of a dual active full-bridge input series-output parallel structure and an MMC-cascaded H-bridge structure.

[0009] Among them, the dual active full-bridge input series-output parallel structure is an efficient DC power conversion system. Its active bridge has the ability to quickly adjust the output current and has good stability and dynamic performance when dealing with sudden load changes. And through high-frequency switching action and soft switching technology, the switching loss is reduced and the overall efficiency is improved. The MMC-cascade H-bridge structure is an important topological form of modular multi-level converter. This structure can handle high-voltage and large-capacity power conversion. Due to the use of sub-module cascading, the dynamic voltage balancing problem caused by the direct series connection of IGBT devices is avoided, and the stability and reliability of the system are improved. At the same time, by controlling the switching state of each sub-module, the precise control of the system output can be achieved.

[0010] Furthermore, in some embodiments, the flexible interconnection component includes a plurality of back-to-back AC / DC converters, wherein a first side of the plurality of back-to-back AC / DC converters is a DC side, and two feeders connected to a second side and a third side of the plurality of back-to-back AC / DC converters belong to the same substation.

[0011] Among them, multiple back-to-back AC / DC converters have significant advantages. First, multiple back-to-back AC / DC converters can flexibly configure the number and connection method of converters according to actual needs to meet different voltage levels and power requirements. Secondly, each converter can be independently controlled and adjusted to achieve precise power conversion and transmission. Finally, in the event of a fault, the faulty converter can be quickly isolated to ensure the normal operation of other converters and the entire system.

[0012] Furthermore, in some embodiments, the plurality of back-to-back AC / DC converters all adopt a two-level VSC structure.

[0013] Among them, the two-level VSC structure is mainly composed of IGBT and a reverse diode connected in parallel with it. The structure is relatively simple and easy to implement and control. At the same time, due to the use of modern power electronic devices such as IGBT, VSC has a lower system cost and higher efficiency.

[0014] Furthermore, in some embodiments, a low-voltage DC distribution line is provided between each back-to-back AC / DC converter and the centralized low-voltage DC bus.

[0015] Among them, the low-voltage DC distribution line mainly connects the back-to-back AC / DC converters and the centralized low-voltage DC bus to ensure that electric energy can be transmitted efficiently and stably between the two. Through this line, the AC / DC converter can convert AC power into DC power and adjust it to a voltage level suitable for the operation of the low-voltage DC bus to meet the power demand of different loads.

[0016] Furthermore, in some embodiments, when the distance between each interconnected system is in a second preset distance interval, the DC conversion component includes: a second setting unit, used to set the centralized medium voltage DC bus based on the first DC power, wherein the lower limit value of the second preset distance interval is greater than or equal to the upper limit value of the first preset distance interval.

[0017] Further, in some embodiments, the flexible interconnect component includes a plurality of three-port PETs, wherein the first side of the plurality of three-port PETs is a DC port, the second side and the third side of the plurality of three-port PETs are both AC ports, and the two feeders connected to the second side and the third side of the plurality of three-port PETs belong to the same station area.

[0018] Among them, the three-port PET is a power electronic transformer with AC and DC interfaces. Through power electronic technology and management of input and output power factors, PET can effectively isolate system faults, ensure the power supply reliability of high-voltage and low-voltage systems, and improve the overall performance of the power system.

[0019] Furthermore, in some embodiments, the medium voltage source converter adopts at least one of a modular multi-level converter structure, a two-level VSC and a three-level VSC.

[0020] Among them, the structure of the modular multilevel converter is mainly composed of multiple cascaded sub-modules with the same structure. What is significantly different from the previous voltage source converter topology is that the MMC has no DC energy storage capacitor between the positive and negative poles on the DC side. Its structural characteristics make it highly modular and scalable, which is convenient for engineering application and maintenance. The multi-level characteristics of the three-level VSC make the three-level VSC closer to a sine wave in the output voltage waveform, thereby reducing the harmonic content and improving the output voltage quality. With its superior performance and reliability, the three-level VSC provides strong support for the stable operation and efficient transmission of the power system.

[0021] The two cross-voltage multi-port distribution network flexible system networking forms of the embodiment of the present invention can directly realize the power transmission and voltage control of the medium-voltage distribution layer and the low-voltage distribution layer, so that the interconnection and interaction effect of the distribution network is significantly enhanced. The large capacity of the medium-voltage layer can be directly used to optimize the low-voltage layer, and the flexible regulation of the low-voltage layer will also be able to enhance the regulation and operation optimization capabilities of the medium-voltage layer. The two cross-voltage multi-port distribution network flexible system networking forms of the embodiment of the present invention can provide multiple interconnection ports to meet the interconnection requirements of multiple stations, multiple feeders, and multiple forms under the new source-load-storage access distribution network. The two cross-voltage multi-port distribution network flexible system networking forms of the embodiment of the present invention are subject to fewer constraints during regulation, operation, and planning analysis. When regulating the interconnected system across voltage levels, it is no longer necessary to perform calculation and analysis of the entire system. It is only necessary to directly regulate the target feeder, which has little impact on other feeders in the system. Therefore, the constraint dimension of the power grid during regulation, operation, and planning analysis is greatly reduced, which is conducive to efficient calculation of operation regulation and planning analysis.

[0022] The cross-voltage multi-port distribution network flexible interconnection system provided by the embodiment of the present invention can utilize the low-voltage DC network to transmit power, and adopt the centralized medium-voltage-low-voltage conversion technology, and utilize the medium-voltage DC network to transmit power, and adopt the decentralized medium-voltage-low-voltage conversion technology, so as to realize the power interaction between the entire flexible interconnection system. It solves the problems of insufficient transmission capacity and operation flexibility in medium and low voltage power supply areas, and improves the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0023] The second aspect of the present invention provides a control method for a cross-voltage multi-port distribution network flexible interconnection system, wherein the method includes the following steps: based on a preset adjustment strategy, using the medium voltage voltage source converter to adjust the reactive power of the first direct current and the first alternating current power grid; and / or, controlling the flexible interconnection components based on dispatching instructions and / or optimization instructions issued by an upper-level dispatching system.

[0024] According to the control method of the cross-voltage multi-port distribution network flexible interconnection system provided by the embodiment of the present invention, it is possible to use the low-voltage DC network to transmit power, and adopt the centralized medium-voltage-low-voltage conversion technology, and use the medium-voltage DC network to transmit power, and adopt the decentralized medium-voltage-low-voltage conversion technology, so as to realize the power interaction between the entire flexible interconnection system. It solves the problems of insufficient transmission capacity and operation flexibility in medium and low voltage power supply areas, and improves the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0025] In summary, the cross-voltage multi-port distribution network flexible interconnection system according to the embodiment of the present invention has the following advantages:

[0026] (1) The two cross-voltage multi-port distribution network flexible system networking forms of the embodiments of the present invention can directly realize the power transmission and voltage control of the medium voltage distribution layer and the low voltage distribution layer, so that the interconnection and interaction effect of the distribution network is significantly enhanced. The large capacity of the medium voltage layer can be directly used to optimize the low voltage layer, and the flexible regulation of the low voltage layer will also be able to enhance the regulation and operation optimization capabilities of the medium voltage layer.

[0027] (2) The two cross-voltage multi-port distribution network flexible system networking forms of the embodiments of the present invention can provide multiple interconnection ports to meet the interconnection requirements of multiple substations, multiple feeders, and multiple forms under the new source-load-storage access distribution network.

[0028] (3) The two cross-voltage multi-port distribution network flexible system networking forms of the embodiments of the present invention are subject to fewer constraints during control operation and planning analysis. When controlling the interconnected system across voltage levels, it is no longer necessary to perform calculation and analysis of the entire system. Only the target feeder needs to be directly controlled, which has little impact on other feeders in the system. Therefore, the constraints of the power grid during control operation and planning analysis are greatly reduced, which is conducive to efficient calculation of operation control and planning analysis.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0031] Figure 1 It is a schematic diagram of the existing single-level flexible interconnection system structure;

[0032] Figure 2 A block diagram of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention;

[0033] Figure 3 This is a structural diagram of a networking form 1 of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention;

[0034] Figure 4 This is a structural diagram of a networking form 2 of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention;

[0035] Figure 5 The present invention is a flow chart of a control method for a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0037] The following describes a cross-voltage multi-port distribution network flexible interconnection system according to an embodiment of the present invention with reference to the accompanying drawings.

[0038] Before introducing the cross-voltage multi-port distribution network flexible interconnection system according to the embodiment of the present invention, a structural diagram of an existing single-level flexible interconnection system is briefly introduced.

[0039] Figure 1 A schematic diagram of the existing single-level flexible interconnection system structure.

[0040] Among them, Figure 1 As shown in the figure, the existing single-level flexible interconnection system includes medium-voltage flexible interconnection components and their corresponding medium-voltage distribution layer and low-voltage flexible interconnection components and their corresponding low-voltage distribution layer. However, in the face of the multi-form, multi-level, and multi-voltage level large-scale access of the new "source-load-storage" in the distribution network, the existing single-level flexible interconnection system does not fully consider the complementary characteristics of medium and low voltage power supply areas in terms of transmission capacity and operational flexibility, and there is a lot of room for improvement in flexibility and planning and operation economy.

[0041] Based on the above problems, an embodiment of the present invention provides a cross-voltage multi-port distribution network flexible interconnection system, which includes two networking forms, wherein networking form 1, a centralized low-voltage bus type cross-voltage multi-port distribution network flexible interconnection system, is suitable for application scenarios where the distance between interconnected systems is relatively short (usually not exceeding 2 km), and networking form 2, a centralized medium-voltage bus type cross-voltage multi-port distribution network flexible interconnection system, is suitable for application scenarios where the distance between interconnected systems is relatively far (usually 2 km to 20 km), thereby solving the problems of insufficient transmission capacity and operation flexibility in medium and low voltage power supply areas, and improving the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0042] Specifically, Figure 2 The present invention is a block diagram of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention.

[0043] like Figure 2 As shown, the cross-voltage multi-port distribution network flexible interconnection system 10 includes: a medium voltage voltage source converter 100, a DC conversion component 200 and a flexible interconnection component 300, wherein the medium voltage voltage source converter 100 is used to convert the first alternating current output by the first alternating current grid into a first direct current; the DC conversion component 200 is used to set a centralized medium voltage DC bus based on the first direct current, or convert the first direct current into a second direct current, and set a centralized low voltage DC bus based on the second direct current, wherein the voltage of the first direct current is higher than the voltage of the second direct current; the first side of the flexible interconnection component 300 is connected to the centralized low voltage DC bus or the centralized medium voltage DC bus, and the second side and the third side of the flexible interconnection component 300 are both connected to the AC system corresponding to the flexible interconnection component 300, and are used to convert the first direct current into the second alternating current, or convert the second direct current into the third alternating current.

[0044] In the embodiment of the present invention, a medium voltage voltage source converter 100 (VSC) can be used to convert the three-phase AC power of the medium voltage distribution bus into medium voltage DC power. Here, the medium voltage VSC can adopt a modular multilevel converter (MMC) structure, a two-level / three-level VSC, and other new medium voltage VSC structures that can meet the control function.

[0045] Among them, the medium-voltage-low-voltage DC transformer is the key equipment to realize the conversion of medium-voltage DC power to low-voltage DC power. It can convert the higher medium-voltage DC voltage into a low-voltage DC voltage suitable for electrical equipment to meet the needs of different voltage levels. It has high efficiency in the power conversion process, can reduce energy loss and improve energy utilization efficiency.

[0046] Furthermore, in some embodiments, Figure 3 As shown, when the distance between each interconnected system is in a first preset distance interval, the DC conversion component 200 includes: a medium voltage-low voltage DC transformer, used to convert the first DC power into the second DC power; and a first setting unit, used to set a centralized low voltage DC bus based on the second DC power.

[0047] in, Figure 3 This is a structural diagram of networking form 1 of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention.

[0048] It should be noted that the networking form 1 of the cross-voltage multi-port distribution network flexible interconnection system is suitable for application scenarios where the distance between the interconnected systems is at a first preset distance (usually not more than 2 km).

[0049] Among them, in some embodiments, the cross-voltage multi-port distribution network flexible interconnection system of the embodiment of the present invention adopts a medium voltage-low voltage DC transformer (DC Transformer, DCT) to convert medium voltage DC power into low voltage DC power, and a centralized low voltage DC bus is set. The medium voltage-low voltage DC transformer of the embodiment of the present invention can adopt at least one of a dual active full-bridge input series-output parallel structure and an MMC-cascade H-bridge structure.

[0050] Furthermore, in some embodiments, the flexible interconnect assembly 300 includes a plurality of back-to-back AC / DC converters, wherein a first side of the plurality of back-to-back AC / DC converters is a DC side, and two feeders connected to a second side and a third side of the plurality of back-to-back AC / DC converters belong to the same substation.

[0051] Specifically, the two feeders connected to the AC ports of each back-to-back AC / DC converter structure belong to the same substation, and the connection between feeders in different substations needs to pass through the low-voltage DC bus link; the interconnection between different back-to-back AC / DC converter structures in the same substation also needs to pass through the low-voltage DC bus link.

[0052] Among them, multiple back-to-back AC / DC converters have significant advantages. First, multiple back-to-back AC / DC converters can flexibly configure the number and connection method of converters according to actual needs to meet different voltage levels and power requirements. Secondly, each converter can be independently controlled and adjusted to achieve precise power conversion and transmission. Finally, in the event of a fault, the faulty converter can be quickly isolated to ensure the normal operation of other converters and the entire system.

[0053] Furthermore, the embodiment of the present invention may interconnect the low-voltage DC bus with multiple AC systems using multiple independent back-to-back AC / DC converter structures, and the low-voltage DC bus is connected to the low-voltage DC side of the back-to-back AC / DC converters.

[0054] In some embodiments, the multiple back-to-back AC / DC converters of the embodiments of the present invention all adopt a two-level VSC structure. A low-voltage DC distribution line is provided between each back-to-back AC / DC converter and the centralized low-voltage DC bus.

[0055] Thus, the construction of the networking form of the centralized low-voltage bus-type cross-voltage multi-port distribution network flexible interconnection system is completed. The networking form 1 of the embodiment of the present invention adopts a low-voltage DC network for power transmission, and at the same time adopts a centralized medium-voltage-low-voltage conversion technology, which has better economy.

[0056] It should be noted that the use of low-voltage DC network in networking form 1 of the cross-voltage multi-port distribution network flexible interconnection system limits the total transmission power of networking form 1. Therefore, when the distance between the interconnected systems is far and the transmission power is large, networking form 2 is more suitable.

[0057] Furthermore, in some embodiments, Figure 4 As shown, when the distance between each interconnected system is in a second preset distance interval, the DC conversion component 200 includes: a second setting unit, used to set a centralized medium voltage DC bus based on the first DC power, wherein the lower limit value of the second preset distance interval is greater than or equal to the upper limit value of the first preset distance interval.

[0058] in, Figure 4 This is a structural diagram of networking form 2 of a cross-voltage multi-port distribution network flexible interconnection system provided according to an embodiment of the present invention.

[0059] Further, in some embodiments, the medium voltage source converter 100 adopts at least one of a modular multi-level converter structure, a two-level VSC and a three-level VSC.

[0060] Among them, Figure 4 As shown, the network form 2 of the embodiment of the present invention adopts a medium voltage voltage source converter 100 to convert the three-phase AC power of the medium voltage distribution bus into medium voltage DC power, and a centralized medium voltage DC bus is set. Here, the medium voltage voltage source converter 100 can adopt a modular multilevel converter MMC structure, a two-level / three-level VSC, and other new medium voltage voltage source converter 100 structures that can meet the control function.

[0061] Furthermore, in some embodiments, the flexible interconnect component 300 includes multiple three-port PETs, wherein the first side of the multiple three-port PETs is a DC port, the second side and the third side of the multiple three-port PETs are both AC ports, and the two feeders connected to the second side and the third side of the multiple three-port PETs belong to the same station area.

[0062] Among them, the two feeders connected to the AC port of each three-port PET belong to the same substation, and the connection between feeders in different substations needs to pass through the medium-voltage DC bus link; the interconnection between different three-port PETs in the same substation also needs to pass through the medium-voltage DC bus link.

[0063] Specifically, the networking form 2 of the embodiment of the present invention uses a three-port power electronic transformer (PET) with one medium-voltage DC port and two low-voltage AC ports to interconnect the medium-voltage DC bus with multiple AC systems, wherein the medium-voltage DC bus is connected to the medium-voltage DC side of the three-port PET, and a medium-voltage DC distribution line may exist between the two. Here, the three-port PET can adopt any converter structure that can complete the control function. For example: a back-to-back structure based on a two-level low-voltage VSC is combined into a three-port PET through a low-voltage DC bus and a low-voltage-medium-voltage DCT.

[0064] Thus, the medium voltage source converter 100 controls the medium voltage side DC bus and the reactive power on the AC side to meet the reactive power support function for the medium voltage AC system. The two AC ports of each independent three-port PET are controlled by Vf network construction, and the control instructions come from the upper scheduling or energy optimization link. The DC voltage on the medium voltage DC side is provided by the medium voltage distribution line, completing the medium voltage-low voltage power interaction function of the entire flexible interconnection system.

[0065] Comparing network form 1 and network form 2, it can be seen that network form 1 uses a low-voltage DC network for power transmission and a centralized medium-voltage-low-voltage conversion technology; network form 2 uses a medium-voltage DC network for power transmission and a decentralized medium-voltage-low-voltage conversion technology. Therefore, in terms of construction cost, network form 1 has better economy. In this way, when the distance between the interconnected systems is short (usually no more than 2km) and the transmission capacity is small (usually less than 500kVA), network form 1 is adopted. However, the use of a low-voltage DC network limits the total transmission power of network form 1. Therefore, when the distance between the interconnected systems is far (usually 2km to 20km) and the transmission power is large (usually greater than 500kVA), network form 2 is more suitable.

[0066] In order to enable relevant practitioners in the field to better understand the cross-voltage multi-port distribution network flexible interconnection system of the embodiment of the present invention, the control strategies of the two networking forms of the cross-voltage multi-port distribution network flexible interconnection system will be explained.

[0067] Among them, the system-level control strategy of the centralized low-voltage bus type cross-voltage multi-port distribution network flexible interconnection system networking form of networking form 1 is as follows: First, the medium-voltage voltage source converter 100 controls its medium-voltage side DC bus and AC side reactive power to meet the reactive support function of the medium-voltage AC system; secondly, the medium-voltage-low-voltage DCT controls the voltage of the centralized low-voltage DC bus to complete the medium-voltage-low-voltage power interaction function of the entire flexible interconnection system. Finally, the two AC ports of each independent back-to-back AC / DC converter structure are controlled by Vf networking, and the control instructions come from the upper-level scheduling or energy optimization link.

[0068] Furthermore, the system-level control strategy of the centralized low-voltage bus-type cross-voltage multi-port distribution network flexible interconnection system networking form of networking form 2 is as follows: first, the medium-voltage voltage source converter 100 controls its medium-voltage side DC bus and AC side reactive power to meet the reactive power support function for the medium-voltage AC system; secondly, the two AC ports of each independent three-port PET adopt Vf networking control, and the control instructions come from the upper-level scheduling or energy optimization link, and the DC voltage on the medium-voltage DC side is provided by the medium-voltage distribution line.

[0069] In this way, the construction and control of two networking forms of cross-voltage multi-port distribution network flexible interconnection system were completed.

[0070] The cross-voltage multi-port distribution network flexible interconnection system provided by the embodiment of the present invention provides power transmission using a low-voltage DC network, while adopting a centralized medium-voltage-low-voltage conversion technology, and power transmission using a medium-voltage DC network, while adopting a decentralized medium-voltage-low-voltage conversion technology, to achieve power interaction between the entire flexible interconnection system. It solves the problems of insufficient transmission capacity and operational flexibility in medium and low voltage power supply areas, and improves the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0071] Next, a control method for a cross-voltage multi-port distribution network flexible interconnection system according to an embodiment of the present invention is described with reference to the accompanying drawings, using the cross-voltage multi-port distribution network flexible interconnection system as described above.

[0072] Figure 5 The present invention is a flow chart of a control method for a cross-voltage multi-port distribution network flexible interconnection system proposed according to an embodiment of the present invention.

[0073] like Figure 5 As shown, the control method of the cross-voltage multi-port distribution network flexible interconnection system includes the following steps:

[0074] In step S501, based on a preset regulation strategy, a medium voltage voltage source converter is used to regulate reactive power of a first direct current and a first alternating current grid.

[0075] In step S502, and / or, the flexible interconnect component is controlled based on the scheduling instruction and / or the optimization instruction issued by the upper scheduling system.

[0076] It should be noted that the above explanation of the embodiment of the cross-voltage multi-port distribution network flexible interconnection system is also applicable to the control method of the cross-voltage multi-port distribution network flexible interconnection system of this embodiment, which will not be repeated here.

[0077] According to the control method of the cross-voltage multi-port distribution network flexible interconnection system provided by the embodiment of the present invention, it is possible to use the low-voltage DC network to transmit power, and adopt the centralized medium-voltage-low-voltage conversion technology, and use the medium-voltage DC network to transmit power, and adopt the decentralized medium-voltage-low-voltage conversion technology, so as to realize the power interaction between the entire flexible interconnection system. It solves the problems of insufficient transmission capacity and operation flexibility in medium and low voltage power supply areas, and improves the flexibility and planning and operation economy of medium and low voltage power supply areas.

[0078] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0079] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0080] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

[0081] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0082] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

Claims

1. A cross-voltage multi-port distribution network flexible interconnection system, characterized in that: include: Medium voltage source converter, DC conversion assembly and flexible interconnect assembly, wherein: The medium voltage source converter is used to convert the first alternating current output by the first alternating current grid into a first direct current; The DC conversion component is used to set a centralized medium-voltage DC bus based on the first DC power, or to convert the first DC power into a second DC power and set a centralized low-voltage DC bus based on the second DC power, wherein the voltage of the first DC power is higher than the voltage of the second DC power; The first side of the flexible interconnection component is connected to the centralized low-voltage DC bus or the centralized medium-voltage DC bus, and the second side and the third side of the flexible interconnection component are both connected to the AC system corresponding to the flexible interconnection component, and are used to convert the first DC power into the second AC power, or convert the second DC power into the third AC power.

2. The cross-voltage multi-port distribution network flexible interconnection system according to claim 1 is characterized in that: When the distance between the interconnected systems is within a first preset distance interval, the DC conversion component includes: a medium voltage-low voltage DC transformer, used for converting the first DC power into the second DC power; The first setting unit is used to set the centralized low-voltage DC bus based on the second DC power.

3. The cross-voltage multi-port distribution network flexible interconnection system according to claim 2 is characterized in that: The medium voltage-low voltage DC transformer adopts at least one of a dual active full-bridge input series-output parallel structure and an MMC-cascade H-bridge structure.

4. The cross-voltage multi-port distribution network flexible interconnection system according to claim 2, characterized in that: The flexible interconnection assembly includes a plurality of back-to-back AC / DC converters, wherein a first side of the plurality of back-to-back AC / DC converters is a DC side, and two feeders connected to a second side and a third side of the plurality of back-to-back AC / DC converters belong to the same substation.

5. The cross-voltage multi-port distribution network flexible interconnection system according to claim 4 is characterized in that: The multiple back-to-back AC / DC converters all adopt a two-level VSC structure.

6. The cross-voltage multi-port distribution network flexible interconnection system according to claim 5, characterized in that: A low-voltage DC power distribution line is arranged between each back-to-back AC / DC converter and the centralized low-voltage DC bus.

7. The cross-voltage multi-port distribution network flexible interconnection system according to claim 1, characterized in that: When the distance between the interconnected systems is within a second preset distance interval, the DC conversion component includes: A second setting unit is used to set the centralized medium voltage DC bus based on the first DC power, wherein a lower limit value of the second preset distance interval is greater than or equal to an upper limit value of the first preset distance interval.

8. The cross-voltage multi-port distribution network flexible interconnection system according to claim 7, characterized in that: The flexible interconnect component includes multiple three-port PETs, wherein the first side of the multiple three-port PETs is a DC port, the second side and the third side of the multiple three-port PETs are both AC ports, and the two feeders connected to the second side and the third side of the multiple three-port PETs belong to the same station area.

9. The cross-voltage multi-port distribution network flexible interconnection system according to any one of claims 1 to 8, characterized in that: The medium voltage source converter adopts at least one of a modular multi-level converter structure, a two-level VSC and a three-level VSC.

10. A control method for a cross-voltage multi-port distribution network flexible interconnection system, characterized in that: A cross-voltage multi-port distribution network flexible interconnection system according to any one of claims 1 to 9 is used, wherein the method comprises the following steps: Based on a preset regulation strategy, using the medium voltage voltage source converter to regulate the reactive power of the first direct current and the first alternating current grid; And / or, the flexible interconnection component is controlled based on a scheduling instruction and / or an optimization instruction issued by an upper scheduling system.

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