Low-voltage flexible interconnection transformer area planning method based on rural photovoltaic direct current access

Abstract

The invention relates to a low-voltage flexible interconnection transformer area planning method based on rural photovoltaic direct current access. The method comprises the following steps: determining a line building mode, an interconnection cable and rated capacities of a transformer area transformer and an interconnection device; based on the determined maximum capacity of the interconnection cable and the rated capacity of the area transformer and the interconnection device, the photovoltaic maximum access capacity is determined in combination with the rural photovoltaic direct current access low-voltage flexible interconnection area capacity configuration principle; and planning the low-voltage flexible interconnection zone area according to the determined line building mode, the rated capacity of the interconnection cable, the rated capacity of the zone area transformer and the rated capacity of the interconnection device, and the photovoltaic maximum access capacity. Safe and stable operation of the power system is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems and their automation, and particularly to a low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access. Background Art

[0002] Distributed photovoltaic grid connection takes the rural scenario as a typical scenario. With the grid connection and access of large-scale distributed photovoltaics, the power quality and operation control of existing distribution substations are affected. On the other hand, the economic structures within the same region are inconsistent, resulting in a large gap in substation loads. Therefore, implementing interconnection and mutual supply for multiple substations through flexible DC technology in the low-voltage substation area system will be a new solution to change the current operation status of substations, improve the power supply level of substations in multiple dimensions, and realize the advanced application functions of substations.

[0003] However, there is a lack of a systematic planning method for low-voltage flexible interconnection substations based on rural photovoltaic DC access. There is a lack of a unified, efficient, and economical planning method in aspects such as line construction, selection of interconnection cables, selection of the rated capacities of transformers and interconnection devices, and configuration of the maximum photovoltaic access capacity. At the same time, under the working conditions of different loads connected to the low-voltage flexible interconnection substation based on rural photovoltaic DC access, due to the limitations of the maximum transmission capacities of electrical equipment such as distribution lines, transformers, and low-voltage flexible interconnection devices, the grid connection and access of a large number of distributed photovoltaics will result in a phenomenon where the load cannot be fully absorbed, leading to the situation of overloading operation of the distribution line, transformer, or the outgoing line of the low-voltage flexible interconnection device, and further resulting in the prominent problem of insecure and unstable operation of the power system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access, which can ensure the normal operation of electrical equipment such as distribution lines, transformers, and low-voltage flexible interconnection devices, thereby ensuring the safe and stable operation of the power system.

[0005] The technical solution adopted by the present invention to solve its technical problem is: to provide a low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access, including the following steps:

[0006] Determine the line construction method, interconnection cables, and the rated capacities of substation transformers and interconnection devices;

[0007] Based on the maximum capacity of the determined interconnection cables and the rated capacities of substation transformers and interconnection devices, determine the maximum photovoltaic access capacity in combination with the capacity configuration principle of the low-voltage flexible interconnection substation based on rural photovoltaic DC access;

[0008] Plan the low-voltage flexible interconnection substation area according to the determined line construction method, interconnection cables, the rated capacities of substation transformers and interconnection devices, and the maximum photovoltaic access capacity.

[0009] The capacity configuration principles for the low-voltage flexible interconnection area with rural photovoltaic DC access include the capacity configuration principles at the area level, the group level, and the system level.

[0010] The capacity configuration principles at the area level include the capacity configuration principle at the area level without considering the load, the capacity configuration principle at the area level considering the lowest AC load during the day in the area, and the capacity configuration principle at the area level considering both the lowest AC load and the lowest DC load during the day in the area;

[0011] Under the capacity configuration principle at the area level without considering the load, the maximum PV access capacity = the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnection cable / 2;

[0012] Under the capacity configuration principle at the area level considering the lowest AC load during the day in the area, the maximum PV access capacity = the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day, and the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device and half of the maximum capacity of the interconnection cable;

[0013] Under the capacity configuration principle at the area level considering both the lowest AC load and the lowest DC load during the day in the area, the maximum PV access capacity = the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day + the lowest DC load during the day, and the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device, half of the maximum capacity of the interconnection cable, and the lowest DC load during the day.

[0014] In the group layer configuration principle, the group layer is the interconnection of k areas, and the group layer configuration principle includes the capacity configuration principle at the group layer without considering the load, the capacity configuration principle at the group layer considering the lowest AC load during the day in the area, and the capacity configuration principle at the group layer considering both the lowest AC load and the lowest DC load during the day in the area;

[0015] Under the capacity configuration principle at the group layer without considering the load, the maximum PV access capacity = k × the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnection cable;

[0016] Under the capacity configuration principle at the group layer considering the lowest AC load during the day in the area, the maximum PV access capacity = k × the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer during the day, and the maximum PV access capacity is less than or equal to the sum of k times the rated capacity of the interconnection device and the maximum capacity of the interconnection cable;

[0017] Under the principle of group layer capacity configuration considering the lowest AC load and the lowest DC load in the daytime of the distribution area, the maximum PV access capacity = k × the maximum load rate of the distribution transformer × the rated capacity of the distribution transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer in the daytime + the lowest DC load of the group layer in the daytime, and the maximum PV access capacity is less than or equal to the sum of k times the rated capacity of the interconnection device, the maximum capacity of the interconnection cable and the lowest DC load of the group layer in the daytime.

[0018] The system layer in the system layer configuration principle is the interconnection of n distribution areas of the system. The system layer configuration principle includes the system layer capacity configuration principle without considering the load, the system layer capacity configuration principle considering the lowest AC load in the daytime of the distribution area, and the system layer capacity configuration principle considering both the lowest AC load and the lowest DC load in the daytime of the distribution area.

[0019] Under the principle of system layer capacity configuration without considering the load, the maximum PV access capacity = n × the maximum load rate of the distribution transformer × the rated capacity of the distribution transformer.

[0020] Under the principle of system layer capacity configuration considering the lowest AC load in the daytime of the distribution area, the maximum PV access capacity = n × the maximum load rate of the distribution transformer × the rated capacity of the distribution transformer + the lowest AC load of the system in the daytime, and the maximum PV access capacity is less than or equal to n times the rated capacity of the interconnection device.

[0021] Under the principle of system layer capacity configuration considering both the lowest AC load and the lowest DC load in the daytime of the distribution area, the maximum PV access capacity = n × the maximum load rate of the distribution transformer × the rated capacity of the distribution transformer + the lowest AC load of the system in the daytime + the lowest DC load of the system in the daytime, and the maximum PV access capacity is less than or equal to the sum of n times the rated capacity of the interconnection device and the lowest DC load of the system in the daytime.

[0022] The line laying method adopts the overhead wiring method, and the line adopts the wiring method of sharing the low-voltage cross arm for AC and DC.

[0023] The interconnection cable uses a double-circuit overhead conductor with a capacity of 720 kW and a cross-sectional area of 240 mm 2 ².

[0024] The rated capacities of the distribution transformer and the interconnection device are both selected as 400 kVA.

[0025] The technical solution adopted by the present invention to solve its technical problems is to provide a low-voltage flexible interconnection distribution area planning device based on rural PV DC access, including:

[0026] The first determination module is used to determine the line laying method, the interconnection cable, and the rated capacities of the distribution transformer and the interconnection device.

[0027] A second determination module, configured to determine the maximum photovoltaic access capacity based on the determined maximum capacity of the interconnection cable, the rated capacities of the substation area transformer and the interconnection device, and in combination with the capacity configuration principle of the low-voltage flexible interconnection substation area for rural photovoltaic DC access;

[0028] A planning module, configured to plan the low-voltage flexible interconnection substation area according to the determined line construction method, the rated capacities of the interconnection cable, the substation area transformer and the interconnection device, and the maximum photovoltaic access capacity.

[0029] The capacity configuration principle of the low-voltage flexible interconnection substation area for rural photovoltaic DC access includes the capacity configuration principle at the substation area layer, the group layer configuration principle, and the system layer configuration principle.

[0030] The capacity configuration principle at the substation area layer includes the capacity configuration principle at the substation area layer without considering the load, the capacity configuration principle at the substation area layer considering the lowest AC load during the day in the substation area, and the capacity configuration principle at the substation area layer considering both the lowest AC load during the day and the lowest DC load during the day in the substation area;

[0031] Under the capacity configuration principle at the substation area layer without considering the load, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2;

[0032] Under the capacity configuration principle at the substation area layer considering the lowest AC load during the day in the substation area, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnection device and half of the maximum capacity of the interconnection cable;

[0033] Under the capacity configuration principle at the substation area layer considering both the lowest AC load during the day and the lowest DC load during the day in the substation area, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day + the lowest DC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnection device, half of the maximum capacity of the interconnection cable, and the lowest DC load during the day.

[0034] The group layer in the group layer configuration principle is a group of k interconnected substations. The group layer configuration principle includes the capacity configuration principle at the group layer without considering the load, the capacity configuration principle at the group layer considering the lowest AC load during the day in the substation area, and the capacity configuration principle at the group layer considering both the lowest AC load during the day and the lowest DC load during the day in the substation area;

[0035] Under the principle of group layer capacity configuration without considering the load, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable;

[0036] Under the principle of group layer capacity configuration considering the lowest AC load during the day in the substation area, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer during the day, and the maximum PV access capacity is less than or equal to k times the sum of the rated capacity of the interconnection device and the maximum capacity of the interconnection cable;

[0037] Under the principle of group layer capacity configuration considering both the lowest AC load during the day and the lowest DC load during the day in the substation area, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer during the day + the lowest DC load of the group layer during the day, and the maximum PV access capacity is less than or equal to k times the sum of the rated capacity of the interconnection device, the maximum capacity of the interconnection cable, and the lowest DC load of the group layer during the day.

[0038] The system layer in the system layer configuration principle is the interconnection of n substation areas in the system. The system layer configuration principle includes the system layer capacity configuration principle without considering the load, the system layer capacity configuration principle considering the lowest AC load during the day in the substation area, and the system layer capacity configuration principle considering both the lowest AC load during the day and the lowest DC load during the day in the substation area;

[0039] Under the principle of system layer capacity configuration without considering the load, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer;

[0040] Under the principle of system layer capacity configuration considering the lowest AC load during the day in the substation area, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the lowest AC load of the system during the day, and the maximum PV access capacity is less than or equal to n times the rated capacity of the interconnection device;

[0041] Under the principle of system layer capacity configuration considering both the lowest AC load during the day and the lowest DC load during the day in the substation area, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the lowest AC load of the system during the day + the lowest DC load of the system during the day, and the maximum PV access capacity is less than or equal to n times the sum of the rated capacity of the interconnection device and the lowest DC load of the system during the day.

[0042] The line laying method determined by the first determination module is the overhead wiring method. Among them, the line adopts the wiring method of sharing the low-voltage cross arm for AC and DC.

[0043] The interconnection cable determined by the first determination module has a capacity of 720 kW and a cross-sectional area of 240 mm 2 for a double-circuit overhead conductor.

[0044] The rated capacities of the distribution transformer and the interconnection device determined by the first determination module are both 400 kVA.

[0045] The technical solution adopted by the present invention to solve its technical problems is to provide an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the above-mentioned low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access are implemented.

[0046] The technical solution adopted by the present invention to solve its technical problems is to provide a computer-readable storage medium with a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access are implemented.

[0047] Beneficial Effects

[0048] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following advantages and positive effects: The present invention provides a capacity configuration principle for low-voltage flexible interconnection substations, which effectively solves the problem of load consumption in low-voltage flexible interconnection substations based on rural photovoltaic DC access, prevents overloading of distribution lines, transformers, and low-voltage flexible interconnection devices, and reasonable capacity configuration improves the maximum capacity of photovoltaic DC access. It not only improves the operation efficiency of the system but also ensures the safe and stable operation of the system, providing an accurate and efficient configuration method for the capacity configuration problem of low-voltage flexible interconnection substations based on rural photovoltaic DC access. The present invention also selects the overhead wiring method, and the line adopts the wiring method of sharing a low-voltage crossarm for AC and DC. In this wiring method, up to two double-circuit lines can be arranged on the DC side, effectively solving the design problem of line construction in low-voltage flexible interconnection distribution substations for rural photovoltaic DC access; the present invention also selects a double-circuit overhead conductor with a capacity of 720 kW and a cross-sectional area of 240 mm 2 which can increase the access capacity of distributed photovoltaics in a single substation area to 680 kWp without considering AC and DC loads. At the same time, it can also ensure that all distributed photovoltaics at any access point are fully consumed or fed into the grid under the conditions of meeting capacity constraints and grouped operation constraints, improving the flexibility of distributed photovoltaic DC grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a flowchart of the low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access according to the first embodiment of the present invention;

[0050] Figure 2It is a schematic structural diagram of the low-voltage flexible interconnection substation area line construction method based on rural photovoltaic DC access in the first embodiment of the present invention;

[0051] Figure 3 It is the capacity configuration diagram of the substation area layer without considering the load in the first embodiment of the present invention;

[0052] Figure 4 It is the capacity configuration diagram of the substation area layer considering the lowest AC load during the day in the first embodiment of the present invention;

[0053] Figure 5 It is the capacity configuration diagram of the substation area layer considering both the lowest AC load and the lowest DC load during the day in the first embodiment of the present invention;

[0054] Figure 6 It is the capacity configuration diagram of the group layer without considering the load in the first embodiment of the present invention;

[0055] Figure 7 It is the capacity configuration diagram of the group layer considering the lowest AC load during the day in the first embodiment of the present invention;

[0056] Figure 8 It is the capacity configuration diagram of the group layer considering both the lowest AC load and the lowest DC load during the day in the first embodiment of the present invention;

[0057] Figure 9 It is the capacity configuration diagram of the system layer without considering the load in the first embodiment of the present invention;

[0058] Figure 10 It is the capacity configuration diagram of the system layer considering the lowest AC load during the day in the first embodiment of the present invention;

[0059] Figure 11 It is the capacity configuration diagram of the system layer considering both the lowest AC load and the lowest DC load during the day in the first embodiment of the present invention. Specific Embodiment

[0060] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0061] The first embodiment of the present invention relates to a low-voltage flexible interconnection substation area planning method based on rural photovoltaic DC access, as Figure 1 shown, including the following steps:

[0062] Step 1, determine the line construction method, interconnection cables, and the rated capacities of the distribution transformer and interconnection device in the substation area.

[0063] The line construction method determined in this step is as Figure 2 shown. Select the overhead wiring method. The line adopts the wiring method of sharing a low-voltage cross arm for AC and DC. In this wiring method, up to two circuits can be arranged on the DC side, thus effectively solving the design problem of the line construction of the low-voltage flexible interconnection distribution transformer area for rural photovoltaic DC access.

[0064] The interconnection cables determined in this step are double-circuit overhead conductors with a capacity of 720 kW and a cross-sectional area of 240 mm 2 . The 240-line is currently the standardized low-voltage insulated conductor with the largest capacity. Under 750 VDC, 1 km can transmit a power capacity of 360 kW, which is close to the capacity of the standardized 400 kVA flexible interconnection device. If a double-circuit 240-line is selected as the flexible interconnection line, without considering AC and DC loads, the access capacity of distributed photovoltaics in a single substation area can be increased to 680 kWp (the substation transformer is 400 kVA, and the photovoltaic grid-connected load rate is calculated based on 80% of the substation transformer capacity), which is 1.7 times the substation transformer capacity. At the same time, it can also ensure that all distributed photovoltaics at any access point are fully consumed or grid-connected under the conditions of meeting the capacity constraint and the group operation constraint, improving the flexibility of distributed photovoltaic DC grid connection. Selecting a thicker line also gives as much distributed photovoltaic grid-connected capacity as possible on the DC side of the substation area.

[0065] The rated capacities of the distribution transformer and interconnection device in the substation area determined in this step are both 400 kVA.

[0066] Step 2, based on the maximum capacity of the determined interconnection cables and the rated capacities of the distribution transformer and interconnection device in the substation area, determine the maximum photovoltaic access capacity in combination with the capacity configuration principle of the low-voltage flexible interconnection substation area for rural photovoltaic DC access.

[0067] In this embodiment, the capacity configuration principles for the low-voltage flexible interconnection substation area for rural photovoltaic DC access include three types: the capacity configuration principle at the substation area layer, the capacity configuration principle at the group layer, and the capacity configuration principle at the system layer.

[0068] Among them, the capacity configuration principle at the substation area layer includes the capacity configuration principle at the substation area layer without considering the load, the capacity configuration principle at the substation area layer considering the lowest AC load during the day in the substation area, and the capacity configuration principle at the substation area layer considering both the lowest AC load and the lowest DC load during the day in the substation area.

[0069] The capacity configuration principle at the substation area layer without considering the load is as follows:

[0070] Taking the interconnection of three substations as an example, as Figure 3As shown, the maximum PV access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 = 0.8 × 400 + 720 / 2 = 680 (kW).

[0071] The capacity configuration principle of the substation area layer when considering the lowest AC load during the day in the substation area is as follows:

[0072] Taking the interconnection of three substations as an example, as Figure 4 shown, the maximum PV access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day = 0.8 × 400 + 720 / 2 + S i = 680 + S i (kW), where S i is the lowest AC load during the day in the substation area; and the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device and half of the maximum capacity of the interconnection cable, that is, the maximum PV access capacity ≤ the rated capacity of the interconnection device + the maximum capacity of the interconnection cable / 2 = 400 + 720 / 2 = 760 (kW).

[0073] The capacity configuration principle of the substation area layer when considering both the lowest AC load and the lowest DC load during the day in the substation area is as follows:

[0074] Taking the interconnection of three substations as an example, as Figure 5 shown, the maximum PV access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day + the lowest DC load during the day = 0.8 × 400 + 720 / 2 + S i + S j = 680 + S i + S j (kW), where S j is the lowest DC load during the day in the substation area; and the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device, half of the maximum capacity of the interconnection cable and the lowest DC load during the day, that is, the maximum PV access capacity ≤ the rated capacity of the interconnection device + the maximum capacity of the interconnection cable / 2 + the lowest DC load during the day = 400 + 720 / 2 + S j = 760 + S j (kW).

[0075] The group layer in the group layer configuration principle is the interconnection of k substations in a group. The group layer configuration principle includes the group layer capacity configuration principle without considering the load, the group layer capacity configuration principle when considering the lowest AC load during the day in the substation area, and the group layer capacity configuration principle when considering both the lowest AC load and the lowest DC load during the day in the substation area.

[0076] The group layer capacity configuration principle without considering the load is as follows:

[0077] Taking the interconnection of six substations as an example, when k = 3, that is, a group of three substations are interconnected and then interconnected with the other three substations. For example, Figure 6 as shown, the maximum PV access capacity = k × the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnection cable = 3 × 0.8 × 400 + 720 = 1680 (kW).

[0078] The principle of group layer capacity configuration considering the lowest AC load during the day in the substation is as follows:

[0079] Taking the interconnection of six substations as an example, when k = 3, that is, a group of three substations are interconnected and then interconnected with the other three substations. For example, Figure 7 as shown, And the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device and the maximum capacity of the interconnection cable multiplied by k, that is, the maximum PV access capacity ≤ k × the rated capacity of the interconnection device + the maximum capacity of the interconnection cable = 400 × 3 + 720 = 1920 (kW).

[0080] The principle of group layer capacity configuration considering both the lowest AC load and the lowest DC load during the day in the substation is as follows:

[0081] Taking the interconnection of six substations as an example, when k = 3, that is, a group of three substations are interconnected and then interconnected with the other three substations. For example, Figure 8 as shown,

[0082] And the maximum PV access capacity is less than or equal to the sum of the rated capacity of the interconnection device, the maximum capacity of the interconnection cable and the lowest DC load of the day group layer, that is,

[0083] In the system layer configuration principle, the system layer is the interconnection of n substations in the system. The system layer configuration principle includes the system layer capacity configuration principle without considering the load, the system layer capacity configuration principle considering the lowest AC load during the day in the substation, and the system layer capacity configuration principle considering both the lowest AC load and the lowest DC load during the day in the substation.

[0084] The system layer capacity configuration principle without considering the load is as follows:

[0085] Taking the interconnection of three substations as an example, that is, when n = 3, as Figure 9 shown, the maximum PV access capacity = n × the maximum load rate of the substation transformer × the rated capacity of the substation transformer = 3 × 0.8 × 400 = 960 (kW).

[0086] The principles for configuring the system layer capacity when considering the lowest AC load during the day in the substation area are as follows:

[0087] Taking the interconnection of three substations as an example, that is, when n = 3, as Figure 10 shown

[0088] And the maximum PV access capacity is less than or equal to n times the rated capacity of the interconnection device, that is, the maximum PV access capacity ≤ n × the rated capacity of the interconnection device = 3 × 400 = 1200 (kW).

[0089] The principles for configuring the system layer capacity when considering both the lowest AC load and the lowest DC load during the day in the substation area are as follows:

[0090] Taking the interconnection of three substations as an example, that is, when n = 3, as Figure 11 shown

[0091] And the maximum PV access capacity is less than or equal to the sum of n times the rated capacity of the interconnection device and the lowest DC load during the day, that is

[0092] Step 3: Plan the low-voltage flexible interconnection substation area according to the determined line construction method, interconnection cables, rated capacities of the substation transformers and interconnection devices, and the maximum PV access capacity.

[0093] It is not difficult to find that based on the capacity configuration principles of the low-voltage flexible interconnection substation area for rural PV DC access with 400 kVA, this embodiment effectively solves the problem of load accommodation in the low-voltage flexible interconnection substation area for rural PV DC access, prevents overloading of distribution lines, substation transformers, and low-voltage flexible interconnection devices. The reasonable capacity configuration improves the maximum capacity of PV DC access, not only enhancing the operation efficiency of the system but also ensuring the safe and stable operation of the system, providing an accurate and efficient configuration method for the capacity configuration problem of the low-voltage flexible interconnection substation area for rural PV DC access. Further, this embodiment also considers the capacity configuration methods of the low-voltage flexible interconnection substation area for rural PV DC access with 400 kVA under different scenarios, and provides calculation methods for the maximum PV access capacity for the cases of not considering the load, considering the lowest AC load during the day, and considering both the lowest AC load and the lowest DC load during the day, improving the accuracy and reliability of the calculation.

[0094] The second embodiment of the present invention relates to a planning device for a low-voltage flexible interconnection substation area based on rural PV DC access, including:

[0095] The first determination module is used to determine the line construction method, the interconnection cable, and the rated capacities of the substation area transformer and the interconnection device;

[0096] The second determination module is used to determine the maximum photovoltaic access capacity based on the maximum capacity of the determined interconnection cable and the rated capacities of the substation area transformer and the interconnection device, in combination with the capacity configuration principle of the low-voltage flexible interconnection substation area for rural photovoltaic DC access;

[0097] The planning module is used to plan the low-voltage flexible interconnection substation area according to the determined line construction method, the interconnection cable, the rated capacities of the substation area transformer and the interconnection device, and the maximum photovoltaic access capacity.

[0098] The capacity configuration principle of the low-voltage flexible interconnection substation area for rural photovoltaic DC access includes the capacity configuration principle at the substation area layer, the group layer configuration principle, and the system layer configuration principle.

[0099] The capacity configuration principle at the substation area layer includes the capacity configuration principle at the substation area layer without considering the load, the capacity configuration principle at the substation area layer considering the lowest AC load during the day in the substation area, and the capacity configuration principle at the substation area layer considering both the lowest AC load and the lowest DC load during the day in the substation area;

[0100] Under the capacity configuration principle at the substation area layer without considering the load, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2;

[0101] Under the capacity configuration principle at the substation area layer considering the lowest AC load during the day in the substation area, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnection device and half of the maximum capacity of the interconnection cable;

[0102] Under the capacity configuration principle at the substation area layer considering both the lowest AC load and the lowest DC load during the day in the substation area, the maximum photovoltaic access capacity = the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable / 2 + the lowest AC load during the day + the lowest DC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnection device, half of the maximum capacity of the interconnection cable, and the lowest DC load during the day.

[0103] In the group layer configuration principle, the group layer is the interconnection of k substations in a group. The group layer configuration principle includes the capacity configuration principle at the group layer without considering the load, the capacity configuration principle at the group layer considering the lowest AC load during the day in the substation area, and the capacity configuration principle at the group layer considering both the lowest AC load and the lowest DC load during the day in the substation area;

[0104] Under the principle of group layer capacity configuration without considering the load, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable;

[0105] Under the principle of group layer capacity configuration considering the lowest AC load during the day in the substation area, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer during the day, and the maximum PV access capacity is less than or equal to k times the sum of the rated capacity of the interconnection device and the maximum capacity of the interconnection cable;

[0106] Under the principle of group layer capacity configuration considering both the lowest AC load and the lowest DC load during the day in the substation area, the maximum PV access capacity = k × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the maximum capacity of the interconnection cable + the lowest AC load of the group layer during the day + the lowest DC load of the group layer during the day, and the maximum PV access capacity is less than or equal to k times the sum of the rated capacity of the interconnection device, the maximum capacity of the interconnection cable and the lowest DC load of the group layer during the day.

[0107] The system layer in the system layer configuration principle is the interconnection of n substation areas of the system. The system layer configuration principle includes the system layer capacity configuration principle without considering the load, the system layer capacity configuration principle considering the lowest AC load during the day in the substation area, and the system layer capacity configuration principle considering both the lowest AC load and the lowest DC load during the day in the substation area;

[0108] Under the principle of system layer capacity configuration without considering the load, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer;

[0109] Under the principle of system layer capacity configuration considering the lowest AC load during the day in the substation area, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the lowest AC load of the system during the day, and the maximum PV access capacity is less than or equal to n times the rated capacity of the interconnection device;

[0110] Under the principle of system layer capacity configuration considering both the lowest AC load and the lowest DC load during the day in the substation area, the maximum PV access capacity = n × the maximum load rate of the substation area transformer × the rated capacity of the substation area transformer + the lowest AC load of the system during the day + the lowest DC load of the system during the day, and the maximum PV access capacity is less than or equal to n times the sum of the rated capacity of the interconnection device and the lowest DC load of the system during the day.

[0111] The line laying method determined by the first determination module is the overhead wiring method. Among them, the line adopts the wiring method of sharing the low-voltage cross arm for AC and DC.

[0112] The interconnection cable determined by the first determination module has a capacity of 720 kW and a cross-sectional area of 240 mm 2 for a double-circuit overhead conductor.

[0113] The rated capacities of the distribution transformer and the interconnection device determined by the first determination module are both 400 kVA.

[0114] The third embodiment of the present invention relates to an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the low-voltage flexible interconnection substation planning method based on rural photovoltaic DC access in the first embodiment are implemented.

[0115] The fourth embodiment of the present invention relates to a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the low-voltage flexible interconnection substation planning method based on rural photovoltaic DC access in the first embodiment are implemented.

[0116] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0117] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0118] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction method that implements the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0119] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to generate a computer-implemented process, thereby providing instructions for implementing the steps of the function specified in one process or multiple processes and / or boxes Figure 1 one process or multiple processes and / or boxes Figure 1 or steps of the function specified in multiple boxes.

[0120] As described above, only the specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for planning low-voltage flexible interconnected areas based on rural photovoltaic DC access, characterized in that: The following steps are involved: Determine the line construction method, interconnection cables, and rated capacity of transformers and interconnection devices in the substation area; Based on the maximum capacity of interconnected cables and the rated capacity of transformers and interconnected devices in the substation, the maximum access capacity of photovoltaic power generation is determined in combination with the capacity configuration principle of low-voltage flexible interconnected substations for rural photovoltaic DC access. The low-voltage flexible interconnected substation is planned based on the determined line construction method, interconnected cables, rated capacity of substation transformers and interconnected devices, and maximum photovoltaic access capacity.

2. The low-voltage flexible interconnection area planning method based on rural photovoltaic DC access according to claim 1 is characterized in that: The low-voltage flexible interconnected substation capacity configuration principles for rural photovoltaic DC access include substation layer capacity configuration principles, group layer configuration principles and system layer configuration principles.

3. The method for planning low-voltage flexible interconnected areas based on rural photovoltaic DC access according to claim 2 is characterized in that: The capacity configuration principle of the substation layer includes the capacity configuration principle of the substation layer when the load is not considered, the capacity configuration principle of the substation layer when the minimum AC load of the substation during the day is considered, and the capacity configuration principle of the substation layer when both the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered; Under the principle of substation capacity configuration without considering the load, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2; Under the principle of substation capacity configuration when considering the minimum AC load in the substation during the day, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2 + the minimum AC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnected device and half of the maximum capacity of the interconnected cable; Under the principle of substation capacity configuration when considering both the minimum AC load and the minimum DC load during the day, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2 + the minimum AC load during the day + the minimum DC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnected device, half of the maximum capacity of the interconnected cable and the minimum DC load during the day.

4. The method for planning low-voltage flexible interconnection areas based on rural photovoltaic DC access according to claim 2 is characterized in that: The group layer in the group layer configuration principle is a group of k interconnected substations, and the group layer configuration principle includes the group layer capacity configuration principle when the load is not considered, the group layer capacity configuration principle when the minimum AC load of the substation during the day is considered, and the group layer capacity configuration principle when both the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered; Under the principle of group capacity configuration without considering the load, the maximum photovoltaic access capacity = k × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + maximum capacity of the interconnected cable; Under the principle of group capacity configuration when considering the lowest AC load in the area during the day, the maximum photovoltaic access capacity = k × the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnected cable + the lowest AC load in the daytime, and the maximum photovoltaic access capacity is less than or equal to the sum of k times the rated capacity of the interconnected device and the maximum capacity of the interconnected cable; Under the principle of group capacity configuration when considering the minimum AC load and the minimum DC load in the daytime, the maximum photovoltaic access capacity = k × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + maximum capacity of the interconnected cable + minimum AC load of the group during the day + minimum DC load of the group during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of k times the rated capacity of the interconnected device, the maximum capacity of the interconnected cable and the minimum DC load of the group during the day.

5. The method for planning low-voltage flexible interconnection areas based on rural photovoltaic DC access according to claim 2 is characterized in that: The system layer in the system layer configuration principle is the interconnection of n substations in the system, and the system layer configuration principle includes the system layer capacity configuration principle when the load is not considered, the system layer capacity configuration principle when the minimum AC load of the substation during the day is considered, and the system layer capacity configuration principle when the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered at the same time; Under the principle of system-level capacity configuration without considering the load, the maximum photovoltaic access capacity = n × the maximum load rate of the transformer in the substation × the rated capacity of the transformer in the substation; Under the system-level capacity configuration principle when considering the lowest AC load in the substation during the day, the maximum photovoltaic access capacity = n × the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the lowest AC load of the system during the day, and the maximum photovoltaic access capacity is less than or equal to n times the rated capacity of the interconnected device; Under the system capacity configuration principle when considering both the minimum AC load and the minimum DC load during the day, the maximum photovoltaic access capacity = n × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + minimum AC load of the system during the day + minimum DC load of the system during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of n times the rated capacity of the interconnected device and the minimum DC load of the system during the day.

6. The method for planning low-voltage flexible interconnection areas based on rural photovoltaic DC access according to claim 1 is characterized in that: The line construction method adopts an overhead wiring method, and the line adopts an AC / DC shared low-voltage cross-arm wiring method.

7. The method for planning low-voltage flexible interconnection areas based on rural photovoltaic DC access according to claim 1 is characterized in that: The interconnection cable has a capacity of 720kW and a cross-sectional area of ​​240mm 2 Double overhead wires.

8. According to the low-voltage flexible interconnected area planning method based on rural photovoltaic DC access according to claim 1, the rated capacity of the area transformer and the interconnection device are both selected to be 400kVA.

9. A low-voltage flexible interconnection area planning device based on rural photovoltaic DC access, characterized in that: include: The first determination module is used to determine the line construction method, interconnection cables, and rated capacity of the transformer and interconnection device in the substation area; The second determination module is used to determine the maximum photovoltaic access capacity based on the determined maximum capacity of the interconnected cables and the rated capacity of the transformer and the interconnection device in the substation area, combined with the capacity configuration principle of the low-voltage flexible interconnected substation area for rural photovoltaic DC access; The planning module is used to plan the low-voltage flexible interconnected substation according to the determined line construction method, interconnected cables, rated capacity of substation transformers and interconnected devices, and maximum photovoltaic access capacity.

10. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 9 is characterized in that: The low-voltage flexible interconnected substation capacity configuration principles for rural photovoltaic DC access include substation layer capacity configuration principles, group layer configuration principles and system layer configuration principles.

11. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 10 is characterized in that: The capacity configuration principle of the substation layer includes the capacity configuration principle of the substation layer when the load is not considered, the capacity configuration principle of the substation layer when the minimum AC load of the substation during the day is considered, and the capacity configuration principle of the substation layer when both the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered; Under the principle of substation capacity configuration without considering the load, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2; Under the principle of substation capacity configuration when considering the minimum AC load in the substation during the day, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2 + the minimum AC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnected device and half of the maximum capacity of the interconnected cable; Under the principle of substation capacity configuration when considering both the minimum AC load and the minimum DC load during the day, the maximum photovoltaic access capacity = the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the maximum capacity of the interconnected cable / 2 + the minimum AC load during the day + the minimum DC load during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of the rated capacity of the interconnected device, half of the maximum capacity of the interconnected cable and the minimum DC load during the day.

12. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 10 is characterized in that: The group layer in the group layer configuration principle is a group of k interconnected substations, and the group layer configuration principle includes the group layer capacity configuration principle when the load is not considered, the group layer capacity configuration principle when the minimum AC load of the substation during the day is considered, and the group layer capacity configuration principle when both the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered; Under the principle of group capacity configuration without considering the load, the maximum photovoltaic access capacity = k × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + maximum capacity of the interconnected cable; Under the principle of group capacity configuration when considering the lowest AC load in the area during the day, the maximum photovoltaic access capacity = k × the maximum load rate of the area transformer × the rated capacity of the area transformer + the maximum capacity of the interconnected cable + the lowest AC load in the daytime, and the maximum photovoltaic access capacity is less than or equal to the sum of k times the rated capacity of the interconnected device and the maximum capacity of the interconnected cable; Under the principle of group capacity configuration when considering the minimum AC load and the minimum DC load in the daytime, the maximum photovoltaic access capacity = k × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + maximum capacity of the interconnected cable + minimum AC load of the group during the day + minimum DC load of the group during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of k times the rated capacity of the interconnected device, the maximum capacity of the interconnected cable and the minimum DC load of the group during the day.

13. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 10 is characterized in that: The system layer in the system layer configuration principle is the interconnection of n substations in the system, and the system layer configuration principle includes the system layer capacity configuration principle when the load is not considered, the system layer capacity configuration principle when the minimum AC load of the substation during the day is considered, and the system layer capacity configuration principle when the minimum AC load of the substation during the day and the minimum DC load of the substation during the day are considered at the same time; Under the principle of system-level capacity configuration without considering the load, the maximum photovoltaic access capacity = n × the maximum load rate of the transformer in the substation × the rated capacity of the transformer in the substation; Under the system-level capacity configuration principle when considering the lowest AC load in the substation during the day, the maximum photovoltaic access capacity = n × the maximum load rate of the substation transformer × the rated capacity of the substation transformer + the lowest AC load of the system during the day, and the maximum photovoltaic access capacity is less than or equal to n times the rated capacity of the interconnected device; Under the system capacity configuration principle when considering both the minimum AC load and the minimum DC load during the day, the maximum photovoltaic access capacity = n × maximum load rate of the transformer in the area × rated capacity of the transformer in the area + minimum AC load of the system during the day + minimum DC load of the system during the day, and the maximum photovoltaic access capacity is less than or equal to the sum of n times the rated capacity of the interconnected device and the minimum DC load of the system during the day.

14. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 9 is characterized in that: The line construction method determined by the first determination module is an overhead wiring method, wherein the line adopts a wiring method in which AC and DC share a low-voltage cross arm.

15. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 9 is characterized in that: The interconnection cable determined by the first determination module has a capacity of 720kW and a cross-sectional area of ​​240mm 2 Double overhead wires.

16. The low-voltage flexible interconnection area planning device based on rural photovoltaic DC access according to claim 9 is characterized in that: The rated capacities of the substation transformer and the interconnection device determined by the first determination module are both 400kVA.

17. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the low-voltage flexible interconnected area planning method based on rural photovoltaic DC access are implemented as described in any one of claims 1-8.

18. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, the steps of the low-voltage flexible interconnected area planning method based on rural photovoltaic DC access as described in any one of claims 1-8 are implemented.

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