A multi-level control method and system for distributed photovoltaic in a low-voltage distribution network substation area

Abstract

The present invention discloses a multi-level control method and system for distributed photovoltaic in a low-voltage distribution network substation area. The method includes: monitoring whether the voltage at the distributed photovoltaic connection point is greater than or equal to the overvoltage threshold. If so, the first to fourth level controls are sequentially executed from low to high in priority order. After each level of control, it is judged whether the current voltage is lower than the overvoltage threshold. If it is lower, the next level of control is not executed. If the current voltage is less than the restoration threshold, the previous control operations are gradually exited in the reverse order of the priority; the first level of control includes load regulation of household appliances in the user's family layer; the second level of control includes load regulation of various adjustable resources in the low-voltage distribution substation area layer; the third level of control includes reactive power regulation of photovoltaic inverters in the photovoltaic grid connection layer; the fourth level of control includes active power regulation of photovoltaic inverters in the photovoltaic grid connection layer. The present invention can effectively reduce the overvoltage caused by the access of distributed photovoltaic in the substation area and improve the access and consumption capacity of distributed photovoltaic.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular, to a multi-level control method and system for distributed photovoltaic in a low-voltage distribution network substation area. Background Art

[0002] With the increase in the penetration rate of photovoltaic in the distribution network, the traditional distribution network power flow will change, and even reverse power flow will occur, resulting in the rise of the voltage at the end of the distribution network. In rural distribution networks with less load, due to the small total load and high photovoltaic penetration rate, the voltage rise phenomenon is more serious. When the voltage rises too high, it will affect the safety of the power grid and easily cause problems such as damage to electrical appliances and the disconnection of photovoltaic inverters from operation. This is also one of the main reasons hindering the increase in the proportion of renewable energy in the power grid.

[0003] Currently, the research on distributed photovoltaic control mainly focuses on group control at the regional level. For the overvoltage problem in the substation area, rigid control and restricting photovoltaic grid connection are mainly used. In some related technologies, the Chinese patent with the publication number CN115149586A proposes a collaborative optimization method and system for distributed energy aggregation control and autonomous control, constructs a joint optimization problem of the total output cost of distributed photovoltaic and power supply reliability, and its control method is photovoltaic active power regulation, and the regulation range is the regional power grid, which cannot solve the overvoltage problem caused by photovoltaic in the substation area. In some other related technologies, the Chinese patent with the publication number CN114465358A discloses a distributed photovoltaic inverter control system and method, gives a physical architecture of a distributed photovoltaic inverter control system, only adjusts the photovoltaic inverter, but does not consider the adjustable load in the home and the adjustable load resources in the substation area, and does not give the calculation method of the adjustment amount and the specific adjustment process, making it difficult to fully explore the adjustment ability of multi-level controllable resources in the distribution network and unable to meet the multi-level coordinated control requirements of distributed photovoltaic.

[0004] Therefore, researching and utilizing the adjustable load in the home and the adjustable load resources in the substation area to transfer the electrical load, absorb the photovoltaic power generation in the substation area, and perform flexible adjustment on the photovoltaic output, and on the premise of ensuring the power supply safety of the substation area, maximizing the utilization of clean energy such as photovoltaic is an important problem that the academic and industrial circles urgently need to solve. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the present invention provides a multi-level control method and system for distributed photovoltaic in a low-voltage distribution network substation area, which fully mobilizes the interactive adjustment ability of household loads and substation area resources, as well as the reactive power adjustment and active power adjustment capabilities of photovoltaic inverters, can effectively reduce the overvoltage caused by the access of distributed photovoltaic in the substation area, ensure power supply safety, and improve the access and absorption capabilities of distributed photovoltaic.

[0006] The present invention adopts the following technical solutions.

[0007] In a first aspect, the present invention provides a multi-level regulation method for distributed photovoltaic in a low-voltage distribution network substation area. The method includes:

[0008] Monitoring whether the voltage at the distributed photovoltaic grid connection point is greater than or equal to a set overvoltage threshold. If so, the first to fourth level regulations are sequentially executed from low to high according to the priority order. After each level of regulation, it is judged whether the current voltage is lower than the overvoltage threshold. If it is lower, the next level of regulation is not executed, and the voltage at the grid connection point is continuously monitored. If the current voltage is less than the set recovery threshold, the previous regulation operations are gradually exited in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; where:

[0009] The first level of regulation includes load regulation of household appliances in the user's home layer;

[0010] The second level of regulation includes load regulation of various adjustable resources in the low-voltage distribution substation area layer;

[0011] The third level of regulation includes reactive power regulation of photovoltaic inverters in the photovoltaic grid connection layer;

[0012] The fourth level of regulation includes active power regulation of photovoltaic inverters in the photovoltaic grid connection layer.

[0013] Optionally, the first level of regulation specifically includes:

[0014] For users with the grid connection point voltage exceeding the overvoltage threshold, it is judged whether their electricity consumption load is less than the photovoltaic power generation power of the user; if it is less, a demand response regulation plan for the first level of regulation strategy is generated according to the adjustable capacity of the household load reported by the user in advance and the user comfort factor, and sent to the user;

[0015] The user selects to start the adjustable appliances in the home or adjust the operating power of the adjustable appliances according to the issued demand response regulation plan to reduce the voltage at the distributed photovoltaic grid connection point.

[0016] Optionally, the demand response regulation plan includes a response period and a target response power, and its calculation formula is as follows:

[0017] P i,dst1 =λ i,1 ×P i,1,max

[0018] In the formula, P i,dst1 represents the target response power for user i in the t response period; P i,t,max represents the adjustable capacity reported by user i; λ i,1 represents the comfort factor reported by user i, 0 ≤ λ i,1 ≤ 1.

[0019] Optionally, the secondary regulation specifically includes:

[0020] Aggregate each of the adjustable resources according to the location information of the overvoltage PV grid connection point and the location information of each adjustable resource, in combination with the topology relationship of the substation area lines;

[0021] Generate the flexible regulation power corresponding to each of the adjustable resources respectively according to the adjustable load capacity and the adjustable proportion coefficient reported by each of the adjustable resources; wherein, each of the adjustable resources includes energy storage input, electric vehicle charging, changing the operation mode of industrial and commercial load equipment to increase the operation power, and transferring the load operation to the current period;

[0022] Based on the flexible regulation power corresponding to each of the adjustable resources, poll each of the adjustable resources in the substation area in turn in the order from near to far from the end of the substation area topology and perform corresponding load regulation to reduce the voltage at the distributed PV grid connection point.

[0023] Optionally, the calculation formula of the flexible regulation power is as follows:

[0024]

[0025] In the formula, P j,2task represents the flexible regulation power of the adjustable resource j; P j represents the single adjustable load capacity of the adjustable resource j; F j is the adjustable proportion coefficient of the adjustable resource j, and F j ≤1.

[0026] Optionally, the tertiary regulation specifically includes:

[0027] Poll each PV inverter in the substation area in turn in the order from near to far from the end of the substation area topology and perform corresponding reactive power regulation; wherein, the expression of the single-time regulation increment of the reactive power regulation for each PV inverter is as follows:

[0028] Q i,调节 = N qi ×Q i,pvmax

[0029]

[0030] In the formula, Q i,调节 represents the single-time reactive power regulation increment of the PV inverter of user i; N qi is the reactive power regulation proportion coefficient of the PV inverter of user i, and N qi ≤1; Q i,pvmax represents the maximum rigid reactive power that the PV inverter of user i can output; S i,pv is the capacity of the PV inverter of user i, and P i,pvIs the active power currently output by the PV inverter of user i.

[0031] Optionally, the four-level regulation specifically includes:

[0032] Poll the PV inverters in the distribution area in turn in the order from near to far from the end of the distribution area topology and perform corresponding active power regulation; among them, the expression of the single-time reduction amount of active power regulation for each PV inverter is as follows:

[0033]

[0034] In the formula, ΔP i,4 Represents the single-time reduction amount of active power of the PV inverter of user i, S reference Is the average declared capacity of all PV inverters in the distribution area, S i,pv Is the declared capacity of user i's PV, ΔP reference Is the set active power regulation value, α i Is the weighted regulation factor of the PV inverter of user i.

[0035] Optionally, the weighted regulation factor, α i The calculation formula is as follows:

[0036]

[0037] In the formula, U i Represents the grid-connected voltage of the PV inverter of user i, U over Represents the overvoltage threshold.

[0038] In a second aspect, the present invention provides a multi-level regulation system for distributed PV in a low-voltage distribution network area, which operates according to the steps of any one of the methods in the first aspect of the present invention. The system includes:

[0039] A monitoring voltage module for monitoring whether the grid-connected voltage of the distributed PV is greater than or equal to the set overvoltage threshold;

[0040] A hierarchical regulation module for, when the monitoring result of the monitoring module is yes, sequentially performing first to fourth level regulations in ascending order of priority, and after each level of regulation, determining whether the current voltage is lower than the overvoltage threshold. If it is lower, the next level of regulation is not performed, and the grid-connected voltage is continuously monitored. If the current voltage is less than the set recovery threshold, the previous regulation operations are gradually exited in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; among them, the hierarchical regulation module includes:

[0041] A first-level regulation unit for performing load regulation on household appliances in the user's home layer;

[0042] The secondary control unit is used to adjust the load of each adjustable resource within the low-voltage distribution substation area layer;

[0043] The tertiary control unit is used to perform reactive power regulation on the photovoltaic inverters in the photovoltaic grid-connected layer;

[0044] The quaternary control unit is used to perform active power regulation on the photovoltaic inverters in the photovoltaic grid-connected layer.

[0045] Thirdly, the present invention also provides a multi-level control system for distributed photovoltaic in a low-voltage distribution network substation area, characterized in that the system includes:

[0046] The home energy gateway is used to monitor the operation status of a single photovoltaic grid connection point and household appliances; wherein, the home energy gateway is communicatively connected to the photovoltaic inverter, smart household appliances, and smart sockets to achieve control of the photovoltaic inverter, smart household appliances, and smart sockets;

[0047] The substation area intelligent terminal is used to report the operation information of electricity consumption, photovoltaic power generation, and adjustable resources of each user within the substation area obtained to the master station, and send the control strategy generated by the master station to the home energy gateway, energy storage, and each adjustable resource within the substation area;

[0048] A processor is provided in the master station for generating the control strategy according to the steps of any one of the first aspects of the present invention.

[0049] The beneficial effects of the present invention are as follows: compared with the prior art:

[0050] The present invention incorporates home adjustable appliances and adjustable load resources in the substation area into the flexible resource package of the substation area, greatly improving the adjustable potential of the substation area. It performs flexible adjustment through a multi-level control method, and performs reactive power regulation and active power output regulation on the photovoltaic inverter based on the topological relationship of the substation area lines. On the premise of ensuring the safety of power supply and consumption, it maximally realizes the grid connection and consumption of distributed photovoltaic; solves the problems of overvoltage, damage to electrical appliances, power supply and consumption safety, and the shutdown of photovoltaic inverters in the substation area with a large number of distributed photovoltaic accesses at present, realizes the autonomous balance of source and load on the substation area side, ensures the power supply safety of the distribution network, and is suitable for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the substation area topology diagram provided by the embodiment of the present invention;

[0052] Figure 2 It is the flowchart of the multi-level control method for distributed photovoltaic in a low-voltage distribution network substation area of the present invention;

[0053] Figure 3 It is the structural schematic diagram of the multi-level control system for distributed photovoltaic in a low-voltage distribution network substation area of the present invention;

[0054] Figure 4 This is the structural principle block diagram of the multi-level control system for distributed photovoltaic in the low-voltage distribution network area of the present invention. Specific embodiments

[0055] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] Embodiment 1:

[0057] The embodiment of the present invention provides a multi-level control method for distributed photovoltaic in the low-voltage distribution network area, including:

[0058] Monitoring whether the voltage at the distributed photovoltaic grid connection point is greater than or equal to the set overvoltage threshold. If so, the first to fourth level controls are sequentially executed from low to high in priority order. After each level of control, it is judged whether the current voltage is lower than the overvoltage threshold. If it is lower, the next level of control is not executed, and the voltage at the grid connection point is continuously monitored. If the current voltage is within the set recovery threshold, the previous control operations are gradually exited in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; where:

[0059] The first level of control includes load regulation of household appliances in the user's home layer;

[0060] The second level of control includes load regulation of various adjustable resources in the low-voltage distribution network area layer;

[0061] The third level of control includes reactive power regulation of photovoltaic inverters in the photovoltaic grid connection layer;

[0062] The fourth level of control includes active power regulation of photovoltaic inverters in the photovoltaic grid connection layer.

[0063] The following combines the Figure 1 topological structure of the low-voltage distribution network area shown to make a specific introduction to the multi-level control method provided by the present invention; Figure 1 Among them, distributed photovoltaics are installed at nodes 3, 11, 19, 25, and 28, with capacities of 5 kW, 5 kW, 5 kW, 10 kW, and 10 kW respectively; the household appliances at nodes 3 and 19 are adjustable, with maximum adjustment capacities of 2 kW and 3 kW respectively; electric vehicle charging piles are installed at nodes 8 and 30, with a charging power of 3 kW; energy storage is installed at node 13, with a charging power of 4 kW.

[0064] As Figure 2As shown in the figure, the distributed photovoltaic multi-level regulation method provided by the embodiment of the present invention includes the following steps:

[0065] S1: Collect the voltage at the photovoltaic grid connection point. In this embodiment, the real-time voltage of each grid connection point is obtained by collecting the meter voltage at the photovoltaic grid connection point in real time.

[0066] S2: Before each level of regulation, judge whether the voltages at the photovoltaic grid connection points of nodes 3, 11, 19, 25, and 28 are greater than or equal to the set voltage threshold. If so, perform the first to fourth level of regulation in ascending order of priority. After each level of regulation, judge whether the voltage is lower than the overvoltage threshold. If it is lower, do not perform the next level of regulation. In this embodiment, the overvoltage threshold U over is set to 242V; if the voltage is within the voltage recovery threshold U restore during the regulation process at each level, gradually exit the regulation operation in the reverse order of the above regulation; in this embodiment, the voltage recovery threshold is set to 235V, and the rated voltage of the power grid is 220V.

[0067] S3: The first-level regulation is to adjust the load of household appliances in the user's home layer.

[0068] Specifically, nodes 3 and 19 have the ability to adjust the load of household appliances in the home layer. Use the home energy gateway to monitor whether the electricity consumption load in the user's home is less than the photovoltaic power generation of this household. If it is less, according to the adjustable capacity P i,1 of the household load reported by the user in advance and the user comfort factor λ i,1 , generate a first-level regulation strategy and send a demand response adjustment plan to the user, including the response time period and the target response power P i,dst1 :

[0069] P i,dst1 =λ i,1 ×P i,1,max

[0070] In the formula, P i,dst1 represents the target response power sent to user i during the t response period; P i,t,max represents the adjustable capacity reported by user i; λ i,1 represents the comfort factor reported by user i, 0 ≤ λ i,1 ≤ 1.

[0071] Furthermore, the user can choose to start the adjustable appliances in the home or adjust the operating power of the appliances, including but not limited to flexible loads such as air conditioners, electric water heaters, and electric heating; the power grid signs a demand response agreement with residential users, and users report information such as adjustable appliances, regulation methods, adjustable capacity, and adjustable time periods that can participate in regulation to the power grid in advance; the power grid issues incentives such as electricity price discounts and green points to users, as well as the time period and power size that need to be adjusted; after the regulation ends, the power grid calculates the user's response volume.

[0072] In a preferred but non-limiting embodiment, the user of Node 3 reports an adjustable capacity of 2 kW and a user comfort factor of 0.8; the user of Node 19 reports an adjustable capacity of 3 kW and a user comfort factor of 0.7. When it is monitored that the voltage at the PV grid connection point of Node 3 exceeds the overvoltage threshold of 242 V, the first-level regulation is initiated, and an adjustment instruction to increase the household load by 2 kW * 0.8 = 1.6 kW is issued. For Node 19 when the voltage exceeds the overvoltage threshold of 242 V, an adjustment instruction to increase the household load by 3 kW * 0.7 = 2.1 kW is issued. After a delay of waiting for a period of time, in this example, 1 minute after the instruction is issued, if the grid connection point voltage still exceeds the overvoltage threshold of 242 V, the second-level regulation is initiated.

[0073] If there is no adjustable load in the household, or the household appliances of the residents do not participate in the adjustment response, there is no first-level regulation, and it jumps to the second-level regulation method.

[0074] S4: The second-level regulation is the load regulation for adjusting adjustable resources such as energy storage and electric vehicle charging at the low-voltage distribution substation area level.

[0075] Specifically, through the substation area intelligent terminal, according to the location information of the overvoltage PV grid connection point and the location information of the adjustable resources, based on the substation area line topology relationship, the adjustable resources that can participate in the adjustment are aggregated; combined with influencing factors such as user willingness, user cooperation degree, and load controllability, a flexible adjustment task P is issued to the adjustable resources in the substation area 2task , including but not limited to energy storage input, electric vehicle charging, changing the operation mode of industrial and commercial load equipment to increase the operating power, transferring the load operation to the current period, etc., polling all adjustable loads in the substation area. Based on the flexible adjustment power corresponding to each of the adjustable resources, the adjustable resources in the substation area are polled in turn in the order from near to far from the end of the substation area topology and the corresponding load adjustment is performed to reduce the voltage at the distributed PV grid connection point. After each adjustment, it is monitored whether the grid connection point is overvoltage. If all grid connection points are lower than the overvoltage threshold, the adjustment of the remaining unadjusted adjustable resources in the substation area is no longer performed.

[0076] Among them, the calculation formula of the flexible adjustment power is as follows:

[0077]

[0078] In the formula, P j,2task represents the flexible adjustment power of the adjustable resource j; P j represents the single adjustable load capacity of the adjustable resource j; F j is the adjustable proportion coefficient of the adjustable resource j, F j ≤ 1.

[0079] In a preferred but non-limiting embodiment, the adjustable proportion coefficient of the charging pile is set to 0.5, and the adjustable proportion coefficient of the energy storage is set to 0.8; then the flexible adjustment tasks of the charging piles at nodes 8 and 30 are 3 kW * 0.5 = 1.5 kW; the flexible adjustment task at the energy storage at node 13 is 4 kW * 0.8 = 3.2 kW. Based on the topological relationship of the distribution network lines, adjustment instructions are sequentially sent to nodes 13, 30, and 8. Wait for a period of time. In this example, 1 minute after the instruction is sent, if the grid connection point voltage still exceeds the overvoltage threshold of 242 V, then the third-level regulation and control is started.

[0080] S5: The third-level regulation and control is the reactive power regulation of the photovoltaic inverters in the photovoltaic grid connection layer.

[0081] Specifically, the adjustable range of the power factor of the photovoltaic inverter is set through the home energy gateway. Within the adjustable range, the power factor is gradually adjusted to output inductive reactive power, and the change of the photovoltaic grid connection point voltage is monitored. When the reactive power reaches its maximum adjustable range, if the voltage still continues to rise, then the next-level regulation and control is executed.

[0082] In this embodiment, the photovoltaic inverters in the distribution network are sequentially polled in the order from near to far from the end of the distribution network topology and corresponding reactive power regulation is performed; among them, the expression of the single adjustment increment for the reactive power regulation of each photovoltaic inverter is as follows:

[0083] Q i,调节 =N qi ×Q i,pvmax

[0084]

[0085] In the formula, Q i,调节 represents the single reactive power adjustment value of the photovoltaic inverter of user i; N qi is the reactive power regulation proportion coefficient of the photovoltaic inverter of user i, N qi ≤1; Q i,pvmax represents the maximum rigid reactive power that the photovoltaic inverter of user i can output; S i,pv is the capacity of the photovoltaic inverter of user i, P i,pv is the active power currently output by the photovoltaic inverter of user i.

[0086] As an embodiment of the present invention, the active power currently output by the photovoltaic inverter at node 3 is 4 kW, and the capacity of the photovoltaic inverter is 5 VA, then N qi is set to 0.2, then Q 3,调节 =0.2×3=0.6 kvar.

[0087] Further, increase the reactive power of the PV inverters at nodes 3, 11, 19, 25, and 28 in sequence according to the order from near to far from the topology end of the substation area. If the voltage still exceeds the overvoltage threshold, start the next round of reactive power regulation until the reactive power reaches its maximum regulation range; when the reactive power reaches its maximum regulation range, if the voltage exceeds the overvoltage threshold, perform the next-level regulation.

[0088] S6: The fourth-level regulation is the active power regulation of the PV inverters in the PV grid-connected layer.

[0089] Specifically, decompose and regulate the power by weighting according to the installed capacity and the current grid connection point voltage, and reduce the active power output ΔP of the PV inverter i,4 , perform polling control on the PVs in the substation area, and monitor the voltage change at the PV grid connection point until the voltage is less than the overvoltage threshold, then it can operate in normal grid connection.

[0090] In a preferred but non-limiting embodiment, poll each PV inverter in the substation area in sequence according to the order from near to far from the topology end of the substation area and perform corresponding active power regulation; among them, the expression of the single-time reduction amount of active power regulation for each of the PV inverters is as follows:

[0091]

[0092] In the formula, ΔP i,4 represents the single-time reduction amount of active power of the PV inverter of user i, S reference is the average declared capacity of all PV inverters in the substation area, S i,pv is the declared PV capacity of user i, ΔP reference is the set active power regulation value, and α i is the weighted regulation factor of the PV inverter of user i:

[0093]

[0094] In the formula, U i represents the grid connection voltage of the PV inverter of user i, and U over represents the overvoltage threshold.

[0095] Further, the grid connection voltage at node 3 is 250V, and S reference is 7kW, then

[0096] ΔP reference = 5%S reference = 0.35kW, The calculation method of the active power regulation amount at other nodes is as above.

[0097]

[0098] ​In this embodiment, the active power output of the PV inverters at nodes 3, 11, 19, 25, and 28 is sequentially reduced in the order from near to far from the end of the topological structure of the substation area. If the voltage still exceeds the overvoltage threshold, the next round of active power regulation is started until the voltage at the node is less than the overvoltage threshold.

[0099] S7: If the voltage is within the recovery threshold during the above-mentioned regulation processes at all levels, the regulation operations are gradually exited in the reverse order of the above-mentioned regulation; in this embodiment, the voltage recovery threshold is configured as 235V.

[0100] The beneficial effects of the present invention are as follows. Compared with the prior art:

[0101] The present invention incorporates the adjustable household appliances and the adjustable load resources in the substation area into the flexible resource package of the substation area, greatly improving the adjustable potential of the substation area. Flexible regulation is carried out through a multi-level regulation method, and reactive power regulation and active power output regulation are performed on the PV inverters based on the topological relationship of the substation area lines. On the premise of ensuring the safety of power supply and consumption, the grid connection and consumption of distributed PV are maximally realized; the problems such as overvoltage, damage to electrical appliances, power supply and consumption safety, and the disconnection of PV inverters in the substation area with a large number of distributed PV accesses are solved, realizing the autonomous balance of source and load on the substation area side, ensuring the power supply safety of the distribution network, and being suitable for popularization and application.

[0102] Embodiment 2:

[0103] As Figure 3 shown, the present invention provides a multi-level regulation system for distributed PV in a low-voltage distribution network substation area. The system specifically includes:

[0104] A household energy gateway for monitoring the operating status of a single PV connection point and household appliances; wherein, the household energy gateway is communicatively connected to the PV inverter, intelligent household appliances, and intelligent sockets to achieve control of the PV inverter, intelligent household appliances, and intelligent sockets; the household energy gateway can also be realized through an IoT electricity meter.

[0105] A substation area intelligent terminal for reporting the operating information of electricity consumption, PV power generation, and adjustable resources of each user in the substation area obtained to the master station, and for sending the regulation strategy generated by the master station to the household energy gateway, energy storage, and each adjustable resource in the substation area.

[0106] A processor is provided in the master station for generating a regulation strategy according to the method in Embodiment 1 above, and for sending the regulation strategy to the substation area intelligent terminal and the household energy gateway to achieve multi-level regulation of distributed PV in the substation area.

[0107] The distributed photovoltaic multi-level regulation system for low-voltage distribution network substations provided by the embodiments of the present invention and the distributed photovoltaic multi-level regulation method for low-voltage distribution network substations provided by Embodiment 1 are based on the same technical concept, and can produce the beneficial effects described in Embodiment 1. For the content not described in detail in this embodiment, reference can be made to Embodiment 1.

[0108] Embodiment 3:

[0109] As Figure 4 shown, the present invention provides a distributed photovoltaic multi-level regulation system for low-voltage distribution network substations. The system is used to implement the steps of the method in Embodiment 1 above. Specifically, the system includes:

[0110] A monitoring voltage module, configured to monitor whether the voltage at the distributed photovoltaic connection point is greater than or equal to a set overvoltage threshold;

[0111] A hierarchical regulation module, configured to, when the monitoring result of the monitoring module is yes, perform first-level to fourth-level regulations in ascending order of priority, and after each level of regulation, determine whether the current voltage is lower than the overvoltage threshold. If it is lower, the next level of regulation is not performed, and the voltage at the connection point is continuously monitored. If the current voltage is less than a set recovery threshold, the previous regulation operations are gradually exited in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; wherein, the regulation module includes:

[0112] A first-level regulation unit, configured to adjust the load of household appliances in the user's home layer;

[0113] A second-level regulation unit, configured to adjust the load of each adjustable resource in the low-voltage distribution substation layer;

[0114] A third-level regulation unit, configured to perform reactive power regulation on the photovoltaic inverters in the photovoltaic grid connection layer;

[0115] A fourth-level regulation unit, configured to perform active power regulation on the photovoltaic inverters in the photovoltaic grid connection layer.

[0116] The distributed photovoltaic multi-level regulation system for low-voltage distribution network substations provided by the embodiments of the present invention and the distributed photovoltaic multi-level regulation method for low-voltage distribution network substations provided by Embodiment 1 are based on the same technical concept, and can produce the beneficial effects described in Embodiment 1. For the content not described in detail in this embodiment, reference can be made to Embodiment 1.

[0117] The present disclosure may be a system, a method, and / or a computer program product. The computer program product may include a computer-readable storage medium having thereon computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0118] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punched card or raised structures in grooves having instructions stored thereon, and any suitable combination of the foregoing. The computer-readable storage medium as used herein is not construed as being a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagated through a waveguide or other transmission medium (e.g., an optical pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0119] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to various computing / processing devices, or downloaded to an external computer or external storage device through a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include a copper transmission cable, an optical fiber transmission, a wireless transmission, a router, a firewall, a switch, a gateway computer, and / or an edge server. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device.

[0120] Computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, executed as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, by using the state information of the computer-readable program instructions to customize an electronic circuit, such as a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit can execute the computer-readable program instructions to implement various aspects of the present disclosure.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area, characterized in that the method include: Monitor whether the voltage of the distributed photovoltaic grid-connected point is greater than or equal to the set overvoltage threshold. If so, perform one to four levels of regulation in order of priority from low to high, and after each level of regulation, determine whether the current voltage is lower than the overvoltage threshold. If so, do not perform the next level of regulation, and continue to monitor the grid-connected point voltage. If the current voltage is lower than the set recovery threshold, gradually exit the previous regulation operation in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; wherein: The first-level regulation includes, for users whose grid connection point voltage exceeds the overvoltage threshold in the user's household layer, when their power load is less than the photovoltaic power generation power of the user, selecting to start the adjustable electrical appliances in the household or adjusting the operating power of the adjustable electrical appliances to perform load regulation; Secondary regulation includes load regulation of various adjustable resources at the low-voltage distribution station area level; The third level of regulation includes reactive power regulation of PV inverters in the PV grid-connected layer; The four-level regulation includes active power regulation of PV inverters in the PV grid-connected layer; The secondary regulation specifically includes: According to the location information of the overvoltage photovoltaic grid-connected point and the location information of each adjustable resource, combined with the topological relationship of the substation line, the adjustable resources are aggregated; Generating the flexible adjustment power corresponding to each of the adjustable resources respectively according to the adjustable load capacity and the dispatchable proportional coefficient reported by each of the adjustable resources; Based on the flexible adjustment power corresponding to each of the adjustable resources, the adjustable resources in the substation are polled in sequence from near to far from the substation topology end and the corresponding load adjustment is performed to reduce the voltage of the distributed photovoltaic grid-connected point.

2. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 1 is characterized in that: The first-level regulation specifically includes: For users whose grid connection point voltage exceeds the overvoltage threshold, determine whether their power load is less than the photovoltaic power generation power of the user; if less, generate a demand response adjustment plan of the first-level control strategy based on the adjustable capacity of the household load and the user comfort factor reported by the user the other day, and send it to the user; The user chooses to start the adjustable electrical appliances in the home or adjust the operating power of the adjustable electrical appliances according to the issued demand response adjustment plan to reduce the voltage of the distributed photovoltaic grid-connected point.

3. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 2 is characterized in that: The demand response adjustment plan includes a response period and a target response power, and its calculation formula is as follows: P i,dst1 =λ i,1 ×P i,1,max Where P i,dst1 represents the target response power sent to user i in response period t; P i,t,max Indicates the adjustable capacity reported by user i; λ i,1 represents the comfort factor reported by user i, 0≤λ i,1 ≤1.

4. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 1 is characterized in that: Each of the adjustable resources includes energy storage input, electric vehicle charging, changing the operating mode of industrial and commercial load equipment to increase operating power, and transferring load operation to the current time period.

5. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 1 is characterized in that: The calculation formula of the flexible adjustment power is as follows: Where, P j,2task represents the flexible adjustment power of adjustable resource j; P j represents the single adjustable load capacity of adjustable resource j; F j is the schedulable proportional coefficient of adjustable resource j, F j ≤1.

6. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 1 is characterized in that: The three-level regulation specifically includes: The photovoltaic inverters in the substation are polled in sequence from near to far from the topological end of the substation area and the corresponding reactive power regulation is performed; wherein the expression of the single adjustment increment for reactive power regulation of each photovoltaic inverter is as follows: Q i,调节 =N qi ×Q i,pvmax In the formula, Q i,调节 Represents the single reactive power adjustment increment of the photovoltaic inverter of user i; N qi is the reactive power regulation proportional coefficient of the photovoltaic inverter of user i, N qi ≤1;Q i,pvmax S represents the maximum rigid reactive power that can be output by the photovoltaic inverter of user i; i,pv is the capacity of the PV inverter of user i, P i,pv is the active power currently output by the PV inverter of user i.

7. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 1 is characterized in that: The four-level regulation specifically includes: The photovoltaic inverters in the substation are polled in sequence from near to far from the topological end of the substation area and the corresponding active power adjustment is performed; wherein the expression of the single reduction amount of active power adjustment for each photovoltaic inverter is as follows: Where ΔP i,4 It represents the single active power reduction of the photovoltaic inverter of user i, S reference is the average declared capacity of all PV inverters in the area, S i,pv is the PV declared capacity of user i, ΔP reference is the set active power adjustment value, α i is the weighted adjustment factor of the PV inverter of user i.

8. The multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area according to claim 7 is characterized in that: The weighted adjustment factor, α i The calculation formula is as follows: Where U i represents the grid-connected voltage of the photovoltaic inverter of user i, U over Indicates the overvoltage threshold.

9. A distributed photovoltaic multi-level control system in a low-voltage distribution network area, running the distributed photovoltaic multi-level control method in a low-voltage distribution network area as claimed in any one of claims 1 to 8, characterized in that: The system includes: The voltage monitoring module is used to monitor whether the voltage at the distributed photovoltaic grid-connected point is greater than or equal to the set overvoltage threshold; A hierarchical control module is used to perform one to four levels of control in order of priority from low to high when the monitoring result of the monitoring module is yes, and after each level of control, determine whether the current voltage is lower than the overvoltage threshold. If so, the next level of control is not performed, and the grid connection point voltage is continuously monitored. If the current voltage is lower than the set recovery threshold, the previous control operation is gradually exited in the reverse order of the priority; the recovery threshold is lower than the overvoltage threshold; wherein the hierarchical control module includes: The primary control unit is used to adjust the load of household appliances in the user's family layer; The secondary control unit is used to adjust the load of each adjustable resource in the low-voltage distribution station area layer; The three-level control unit is used to perform reactive power regulation on the photovoltaic inverter in the photovoltaic grid-connected layer; The four-level control unit is used to adjust the active power of the photovoltaic inverter in the photovoltaic grid-connected layer.

10. A distributed photovoltaic multi-level control system in a low-voltage distribution network area, characterized in that the system include: A home energy gateway is used to monitor the operating status of a single photovoltaic grid-connected point and household appliances; wherein the home energy gateway is connected to the photovoltaic inverter, smart household appliances and smart sockets in communication to achieve control of the photovoltaic inverter, smart household appliances and smart sockets; The intelligent terminal in the substation area is used to report the operation information of each user's electricity consumption, photovoltaic power generation and adjustable resources in the substation area to the master station, and send the control strategy generated by the master station to the home energy gateway, energy storage and various adjustable resources in the substation area; The master station is provided with a processor for generating the control strategy according to the multi-level control method for distributed photovoltaic power generation in a low-voltage distribution network area as described in any one of claims 1 to 8.

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