Flexible voltage regulation method and system for low-voltage power distribution network

Abstract

The invention discloses a low-voltage distribution network flexible voltage regulation method and system, and the method comprises the steps: S1, the AC side of an AC-DC converter Cn (n = 1, 2,..., N) is connected in parallel to a low-voltage AC distribution network, the DC side is connected in parallel to a DC line, and the AC-DC converter C1 is close to the power supply side and is started to operate in a DC constant voltage control mode; starting the AC / DC converter Cn (n = 2,..., N) to operate in a constant power control mode; s2, the AC-DC converter Cn (n = 2,..., N) collects AC side voltage; if the AC side voltage is lower than a set voltage threshold lower limit, the AC-DC converter sends active power to an AC line; if the AC side voltage is higher than a set voltage threshold upper limit, the AC-DC converter absorbs active power from an AC line; and if the AC side voltage is within the set threshold range, the AC-DC converter is in a standby state. According to the invention, the problems of low voltage caused by long distance of the low-voltage distribution network, heavy load of lines and overvoltage caused by distributed photovoltaics are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent power distribution, and in particular relates to a flexible voltage regulation method and system for a low-voltage distribution network. Background Art

[0002] The low-voltage distribution network is at the end of the power grid. Due to long lines and seasonal load fluctuations, low voltage problems for users have long existed. The widespread access of distributed photovoltaics to the low-voltage distribution network has gradually highlighted the problem of overvoltage due to the inability to locally absorb and send back to the substation. Voltage quality is a key factor affecting the user's electricity experience, and improving voltage quality is an important work goal of power supply companies. Due to the combined influence of seasonal load fluctuations, distributed photovoltaic access and other factors, methods such as voltage regulating transformers and reactive power compensators cannot meet the needs of bidirectional voltage regulation, and the difficulty of bidirectional voltage over-limit control has gradually increased.

[0003] The Chinese patent with publication number CN115912492A discloses a method for controlling the voltage of the grid connection point of a distribution network considering large-scale distributed power sources, which specifically relates to the field of power control technology. The method includes: obtaining the voltage value of the public grid connection point, the active power and reactive power of each distributed power source entering the public grid connection point; when the difference between the voltage value of the public grid connection point and the reference voltage is greater than the first threshold, calculating the reactive output limit connected to each distributed power source; according to the difference between the voltage value of the public grid connection point and the reference voltage, obtaining the total reactive control amount; according to the total reactive control amount and the reactive output limit of each distributed power source, adjusting the reactive control instructions of each power branch to control each distributed power source to respond to reactive output according to the adjusted reactive control instructions. Although the invention can theoretically realize the bidirectional voltage regulation of the distribution network, it mainly focuses on the voltage adjustment of the public grid connection point, and cannot directly adjust the load points independently. And there may be a response delay in the reactive power adjustment of the distributed power source. Rapidly changing loads and generation conditions may cause the voltage regulation to be insufficiently timely, thereby affecting voltage stability. Summary of the invention

[0004] The present invention provides a low-voltage distribution network flexible voltage regulation method and system, aiming to solve the problems of low voltage caused by long distance low-voltage distribution network, line overload, and overvoltage caused by distributed photovoltaic.

[0005] In order to solve the above technical problems, the present invention provides a low-voltage distribution network flexible voltage regulation method, comprising the following steps:

[0006] S1: The AC side of the AC-DC converter C_n (n=1, 2, ..., N) is connected in parallel to the low-voltage AC distribution network, and the DC side is connected in parallel to the DC line. The AC-DC converter C_1 is close to the power supply side and is started to operate in the DC constant voltage control mode. The AC-DC converter C_n (n=2, ..., N) is started to operate in the constant power control mode.

[0007] S2: AC-DC converter C_n (n=2,…,N) collects the AC side voltage U C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n (n=2,…,N)∈[U up ,U down ], the AC / DC converter C_n (n=2,…,N) is in standby state.

[0008] Preferably, the active power of the DC converter should satisfy:

[0009]

[0010] Where P C_n is the active power flowing into the DC line from AC / DC converter n, N is the number of AC / DC converters, P loss is the loss of the DC line, and t is the time.

[0011] Preferably, the AC / DC converter emits or absorbs active power P_n, n=2, ..., N, which should satisfy:

[0012]

[0013] Where P C_n is the active power; ΔU is the AC side voltage U of the AC / DC converter C_n (n=2,…,N) C_n (n=2,…,N) and the set voltage threshold upper limit or voltage threshold lower limit; r is the AC line resistance between the AC / DC converter C_n (n=2,…,N) grid connection point and the head end of the substation.

[0014] Preferably, the AC / DC converter realizes remote off-grid connection and power control specifically as follows:

[0015] The AC / DC converters communicate with each other via a DC carrier.

[0016] The AC / DC converter C_1 obtains the operating status and data of the AC / DC converter C_n (n=2, ..., N), and sends it to the edge computing terminal via AC carrier communication.

[0017] The AC / DC converter C_1 receives control instructions sent by the edge computing terminal to achieve remote off-grid and power control of the AC / DC converter C_n (n=2, ..., N).

[0018] Preferably, the AC / DC converter realizes remote off-grid control specifically as follows:

[0019] The edge computing terminal issues off-grid control instructions.

[0020] The AC / DC converter C_1 receives the off-grid control instruction and issues the off-grid control instruction to the AC / DC converter C_n (n=2, ..., N).

[0021] The AC / DC converter C_n (n=2, ..., N) receives the off-grid control instruction, stops power output, and transmits a shutdown signal to the AC / DC converter C_1.

[0022] The AC-DC converter C_1 receives the shutdown signal and shuts down when detecting that the DC side power is zero.

[0023] On the other hand, the present invention provides a flexible voltage regulation system for a low-voltage distribution network, comprising a configuration module and a voltage regulation module.

[0024] A configuration module is provided for connecting the AC side of the AC-DC converter C_n (n=1, 2, ..., N) in parallel to a low-voltage AC distribution network, and the DC side in parallel to a DC line. The AC-DC converter C_1 is close to the power supply side and is started to operate in a DC constant voltage control mode, and the AC-DC converter C_n (n=2, ..., N) is started to operate in a constant power control mode.

[0025] The voltage regulation module is used to collect the AC side voltage U of the AC / DC converter C_n (n=2, ..., N) C_n (n=2,…,N) for identification and adjustment; if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n(n=2,…,N)∈[U up ,U down ], the AC / DC converter C_n (n=2,…,N) is in standby state.

[0026] Preferably, the active power of the AC / DC converter in the configuration module should satisfy:

[0027]

[0028] Where P C_n is the active power flowing into the DC line from AC / DC converter n, N is the number of AC / DC converters, P loss is the loss of the DC line, and t is the time.

[0029] Preferably, the AC / DC converter in the voltage regulation module emits or absorbs active power P_n, n=2, ..., N, which should satisfy:

[0030]

[0031] Where P C_n is the active power; ΔU is the AC side voltage U of the AC / DC converter C_n (n=2,…,N) C_n (n=2,…,N) and the set voltage threshold upper limit or voltage threshold lower limit; r is the AC line resistance between the AC / DC converter C_n (n=2,…,N) grid connection point and the head end of the substation.

[0032] Preferably, the voltage regulation module can also realize remote off-grid connection and power control of the AC / DC converter, specifically:

[0033] The AC / DC converters communicate with each other via a DC carrier.

[0034] The AC / DC converter C_1 obtains the operating status and data of the AC / DC converter C_n (n=2, ..., N), and sends it to the edge computing terminal via AC carrier communication.

[0035] The AC / DC converter C_1 receives control instructions sent by the edge computing terminal to achieve remote off-grid and power control of the AC / DC converter C_n (n=2, ..., N).

[0036] The AC / DC converter realizes remote off-grid control specifically as follows:

[0037] The edge computing terminal issues off-grid control instructions.

[0038] The AC / DC converter C_1 receives the off-grid control instruction and issues the off-grid control instruction to the AC / DC converter C_n (n=2, ..., N).

[0039] The AC / DC converter C_n (n=2, ..., N) receives the off-grid control instruction, stops power output, and transmits a shutdown signal to the AC / DC converter C_1.

[0040] The AC-DC converter C_1 receives the shutdown signal and shuts down when detecting that the DC side power is zero.

[0041] On the other hand, the present invention also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the low-voltage distribution network flexible voltage regulation method as described in any embodiment of the present invention is implemented.

[0042] On the other hand, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for flexible voltage regulation of a low-voltage distribution network as described in any embodiment of the present invention is implemented.

[0043] Compared with the prior art, the present invention has the following technical effects:

[0044] The flexible voltage regulation method and system for low-voltage distribution network proposed in the present invention ensures the stability of DC side voltage by operating the DC converter close to the power supply side in DC constant voltage control mode, thus providing basic stability for the system; other AC / DC converters operate in constant power control mode, and can be adjusted according to the real-time changes of AC side voltage, effectively coping with load fluctuations and grid imbalance. The real-time voltage monitoring and regulation mechanism improves the system's responsiveness to various power loads and external disturbances, and improves the overall reliability and operational flexibility of the distribution network. It can effectively solve problems such as low voltage caused by long distance of low-voltage distribution network, heavy line load, and overvoltage caused by distributed photovoltaics, and improve the power supply capacity and voltage quality of low-voltage distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is an overall flow chart of the flexible voltage regulation method for low-voltage distribution network according to the present invention;

[0046] Figure 2 It is a schematic diagram of the connection of the AC / DC converter circuits of the present invention;

[0047] Figure 3 is a control structure diagram of the AC-DC converter C_1 of the present invention;

[0048] Figure 4 is a control structure diagram of the AC / DC converter C_n (n=2, ..., N) of the present invention;

[0049] Figure 5 It is an overall flow chart of the AC / DC converter of the present invention to realize remote off-grid control;

[0050] Figure 6 is an input voltage and current waveform diagram of the AC-DC converter C_1 described in the present invention;

[0051] Figure 7 1 is an output voltage and current waveform diagram of the AC / DC converter C_2 described in the present invention. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in combination with specific embodiments of the present application and with reference to the accompanying drawings.

[0053] Embodiment 1

[0054] This embodiment provides a low voltage distribution network flexible voltage regulation method, see Figure 1 As shown, the following steps are included:

[0055] S1: See Figure 2 As shown, the AC-DC converter C_n (n=1, 2, ..., N) is connected in parallel to the low-voltage AC distribution network on the AC side and in parallel to the DC line on the DC side. The AC-DC converter C_1 is close to the power supply side and is started to operate in the DC constant voltage control mode to ensure the stability of the DC side; the AC-DC converter C_n (n=2, ..., N) is started to operate in the constant power control mode.

[0056] S2: AC-DC converter C_n (n=2,…,N) collects the AC side voltage U C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n (n=2,…,N)∈[U up ,U down ], the AC-DC converter C_n (n=2, ..., N) is in standby mode. The AC-DC converter calculates the active power P emitted or absorbed locally C_n (n=2,…,N) size to achieve real-time adjustment of AC side voltage.

[0057] As a preferred implementation of this embodiment, refer to Figure 3 , 4 As shown in the figure, it is the control structure diagram of the AC-DC converter C_n (n=1,2,…,N). The AC-DC converter C_n (n=1,2,…,N) adopts a dual closed-loop control structure, namely a voltage outer loop and a current inner loop. The voltage outer loop of the AC-DC converter C_1 adopts PI control to achieve voltage stabilization and voltage balancing control of the DC bus. In order to improve the output steady-state accuracy of the AC-DC converter C_n (n=2,…,N) and reduce the grid voltage interference, the voltage outer loop can adopt a quasi-PR control method to achieve precise regulation of the terminal output voltage and suppression of harmonic components. In order to improve the stability of system control and the dynamic response of the load, the current inner loop of the AC-DC converter C_n (n=1,2,…,N) can adopt a hysteresis control method.

[0058] As a preferred implementation of this embodiment, the active power of the DC converter should satisfy:

[0059]

[0060] Where P C_n is the active power flowing into the DC line from AC / DC converter n, N is the number of AC / DC converters, P loss is the loss of the DC line, and t is the time.

[0061] As a preferred implementation of this embodiment, before the low-voltage distribution network flexible voltage regulation system is connected, the voltage at the grid connection point of the AC / DC converter is:

[0062]

[0063] Where U C_n is the grid connection point voltage of the AC / DC converter; U o is the grid connection point voltage of the AC / DC converter C_1; r and x are the AC line resistance and reactance between the grid connection point of the AC / DC converter C_n (n=1,2,…,N) and the head end of the substation; P L and Q L It is the user's active power and reactive power.

[0064] After the low-voltage distribution network flexible voltage regulation system is connected, the voltage at the grid connection point of the AC / DC converter is:

[0065]

[0066] Where P and Q are the active power and reactive power of the AC line.

[0067] Therefore, the AC / DC converter emits or absorbs active power P_n, n=2, ..., N, which should satisfy:

[0068]

[0069] Where P C_n is the active power; ΔU is the AC side voltage U of the AC / DC converter C_n (n=2,…,N) C_n (n=2,…,N) and the set voltage threshold upper limit or voltage threshold lower limit; r is the AC line resistance between the AC / DC converter C_n (n=2,…,N) grid connection point and the head end of the substation.

[0070] As a preferred implementation of this embodiment, the AC / DC converter realizes remote off-grid connection and power control through the edge computing terminal. Combining the intelligent decision-making ability of the edge computing terminal and the automatic response of the AC / DC converter, more efficient and intelligent power management and control can be achieved to adapt to complex and changeable power demand and environmental conditions. Specifically:

[0071] The AC / DC converters communicate with each other via a DC carrier.

[0072] The AC / DC converter C_1 obtains the operating status and data of the AC / DC converter C_n (n=2, ..., N), and sends it to the edge computing terminal via AC carrier communication.

[0073] The AC / DC converter C_1 receives control instructions sent by the edge computing terminal to achieve remote off-grid and power control of the AC / DC converter C_n (n=2, ..., N).

[0074] Through the control instructions issued by the edge computing terminal, the AC-DC converter C_1 can centrally manage and optimize the off-grid and power output of other converters. This centralized control helps to coordinate the operations of different AC-DC converters and ensure overall stability and efficiency.

[0075] As a preferred implementation of this embodiment, the AC / DC converter realizes remote off-grid control specifically as follows:

[0076] The edge computing terminal issues off-grid control instructions.

[0077] The AC / DC converter C_1 receives the off-grid control instruction and issues the off-grid control instruction to the AC / DC converter C_n (n=2, ..., N).

[0078] The AC / DC converter C_n (n=2, ..., N) receives the off-grid control instruction, stops power output, and transmits a shutdown signal to the AC / DC converter C_1.

[0079] The AC-DC converter C_1 receives the shutdown signal and shuts down when detecting that the DC side power is zero.

[0080] Through the orderly off-grid control process, each AC / DC converter will stop power output and send a shutdown signal after receiving the off-grid command, and the AC / DC converter C_1 will not shut down until it confirms that all AC / DC converters have stopped working, so as to improve safety and stability.

[0081] In order to verify the effectiveness and superiority of the method provided in this embodiment, some specific cases are provided below:

[0082] The experimental environment is configured with two AC / DC converters (rated power of 50kW each), the AC side voltage is 380V, and the user load switching is 10kW. This experiment verifies that the method proposed in this embodiment can achieve grid side voltage control under load changes and maintain grid voltage stability. Figure 6 , Figure 7 As shown, the input voltage and current waveforms of the AC / DC converter C_1 and the output voltage and current waveforms of C_2 of the flexible voltage regulation system of the low-voltage distribution network in this experiment when the user load increases by 10kW.

[0083] Embodiment 2

[0084] Accordingly, this embodiment provides a low-voltage distribution network flexible voltage regulation system, including a configuration module and a voltage regulation module.

[0085] A configuration module is provided for connecting the AC side of the AC-DC converter C_n (n=1, 2, ..., N) in parallel to the low-voltage AC distribution network, and the DC side in parallel to the DC line. The AC-DC converter C_1 is close to the power supply side and is started to operate in a DC constant voltage control mode. The AC-DC converter C_n (n=2, ..., N) is started to operate in a constant power control mode. This module is used to implement the function of step S1 in the first embodiment, which will not be described in detail here.

[0086] The voltage regulation module is used to collect the AC side voltage U of the AC / DC converter C_n (n=2, ..., N) C_n (n=2,…,N) for identification and adjustment; if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n (n=2,…,N)∈[U up ,U down], the AC / DC converter C_n (n=2,…,N) is in standby state. This module is used to implement the function of step S2 in embodiment 1, which will not be described in detail here.

[0087] Embodiment 3

[0088] This embodiment provides an electronic device, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the low-voltage distribution network flexible voltage regulation method as described in any embodiment of the present invention is implemented.

[0089] Embodiment 4

[0090] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the low-voltage distribution network flexible voltage regulation method as described in any embodiment of the present invention is implemented.

[0091] In the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, c can be single or multiple.

[0092] Those of ordinary skill in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented in a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0093] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0094] In several embodiments provided in the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), disk or optical disk, and other media that can store program codes.

[0095] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A low voltage distribution network flexible voltage regulation method, characterized in that: The following steps are involved: S1: The AC-DC converter C_n (n=1, 2, ..., N) is connected in parallel to the low-voltage AC distribution network on the AC side and connected in parallel to the DC line on the DC side. The AC-DC converter C_1 is close to the power supply side and is started to operate in the DC constant voltage control mode. The AC-DC converter C_n (n=2, ..., N) is started to operate in the constant power control mode. S2: AC-DC converter C_n (n=2,…,N) collects the AC side voltage U C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n (n=2,…,N)∈[U up ,U down ], the AC / DC converter C_n (n=2,…,N) is in standby state.

2. The low voltage distribution network flexible voltage regulation method according to claim 1, characterized in that: The active power of the AC / DC converter should meet the following requirements: Where P C_n is the active power flowing into the DC line from AC / DC converter n, N is the number of AC / DC converters, P loss is the loss of the DC line, and t is the time.

3. The low voltage distribution network flexible voltage regulation method according to claim 1, characterized in that: The AC / DC converter emits or absorbs active power P_n, n=2, ..., N, which should satisfy: Where P C_n is the active power; ΔU is the AC side voltage U of the AC / DC converter C_n (n=2,…,N) C_n (n=2,…,N) and the set voltage threshold upper limit or voltage threshold lower limit; r is the AC line resistance between the AC / DC converter C_n (n=2,…,N) grid connection point and the head end of the substation.

4. The low voltage distribution network flexible voltage regulation method according to claim 1, characterized in that: The AC / DC converter realizes remote off-grid connection and power control specifically as follows: The AC / DC converters communicate with each other via a DC carrier; The AC / DC converter C_1 obtains the operating status and data of the AC / DC converter C_n (n=2, ..., N), and sends it to the edge computing terminal via AC carrier communication; The AC / DC converter C_1 receives control instructions sent by the edge computing terminal to achieve remote off-grid and power control of the AC / DC converter C_n (n=2, ..., N).

5. The low voltage distribution network flexible voltage regulation method according to claim 4, characterized in that: The AC / DC converter realizes remote off-grid control specifically as follows: The edge computing terminal issues off-grid control instructions; The AC / DC converter C_1 receives the off-grid control instruction and issues the off-grid control instruction to the AC / DC converter C_n (n=2,…,N); The AC / DC converter C_n (n=2, ..., N) receives the off-grid control command, stops power output, and transmits a shutdown signal to the AC / DC converter C_1; The AC-DC converter C_1 receives the shutdown signal and shuts down when detecting that the DC side power is zero.

6. A low voltage distribution network flexible voltage regulation system, characterized in that: Includes a configuration module and a voltage regulation module; A configuration module is used to connect the AC side of the AC-DC converter C_n (n=1, 2, ..., N) in parallel to the low-voltage AC distribution network, and the DC side in parallel to the DC line. The AC-DC converter C_1 is close to the power supply side and starts to operate in a DC constant voltage control mode, and the AC-DC converter C_n (n=2, ..., N) is started to operate in a constant power control mode; The voltage regulation module is used to collect the AC side voltage U of the AC / DC converter C_n (n=2, ..., N) C_n (n=2,…,N) for identification and adjustment; if the AC side voltage U C_n (n=2,…,N) is lower than the set voltage threshold U down , the AC / DC converter C_n (n=2,…,N) sends active power P to the AC line C_n (n=2,…,N); if the AC side voltage U C_n (n=2,…,N) is higher than the set voltage threshold upper limit U up , the AC / DC converter C_n (n=2,…,N) absorbs active power P from the AC line C_n (n=2,…,N); if the AC side voltage is within the set threshold range, that is, U C_n (n=2,…,N)∈[U up ,U down ], the AC / DC converter C_n (n=2,…,N) is in standby state.

7. The low voltage distribution network flexible voltage regulation system according to claim 6, characterized in that: The active power of the AC / DC converter in the configuration module should meet the following requirements: Where P C_n is the active power flowing into the DC line from AC / DC converter n, N is the number of AC / DC converters, P loss is the loss of the DC line, and t is the time.

8. The low voltage distribution network flexible voltage regulation system according to claim 6, characterized in that: The AC / DC converter in the voltage regulation module emits or absorbs active power P_n, n=2, ..., N, which should satisfy: Where P C_n is the active power; ΔU is the AC side voltage U of the AC / DC converter C_n (n=2,…,N) C_n (n=2,…,N) and the set voltage threshold upper limit or voltage threshold lower limit; r is the AC line resistance between the AC / DC converter C_n (n=2,…,N) grid connection point and the head end of the substation.

9. The low voltage distribution network flexible voltage regulation system according to claim 6, characterized in that: The voltage regulation module can also realize the AC / DC converter to achieve remote off-grid connection and power control, specifically: The AC / DC converters communicate with each other via a DC carrier; The AC / DC converter C_1 obtains the operating status and data of the AC / DC converter C_n (n=2, ..., N), and sends it to the edge computing terminal via AC carrier communication; The AC / DC converter C_1 receives the control command sent by the edge computing terminal to realize remote off-grid connection and power control of the AC / DC converter C_n (n=2,…,N); The AC / DC converter realizes remote off-grid control specifically as follows: The edge computing terminal issues off-grid control instructions; The AC / DC converter C_1 receives the off-grid control instruction and issues the off-grid control instruction to the AC / DC converter C_n (n=2,…,N); The AC / DC converter C_n (n=2, ..., N) receives the off-grid control command, stops power output, and transmits a shutdown signal to the AC / DC converter C_1; The AC-DC converter C_1 receives the shutdown signal and shuts down when detecting that the DC side power is zero.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the low-voltage distribution network flexible voltage regulation method according to any one of claims 1 to 5 is implemented.

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