Distributed photovoltaic reverse power transmission scheduling plan determination method and device

Abstract

The invention relates to a distributed photovoltaic reverse power transmission scheduling plan determination method and device, and belongs to the field of photovoltaic power generation scheduling plans. According to the result of the initial power generation scheduling plan, whether the feeder lines and the substations have reverse power transmission phenomena or not is judged, when only the feeder lines have the reverse power transmission phenomena, the feeder lines which do not allow the reverse power transmission currently are controlled to reduce the distributed power generation power, and when the feeder lines and the substations have the reverse power transmission phenomena, the power generation power of the feeder lines which do not allow the reverse power transmission currently is reduced. And if the current transformer station still has the reverse power transmission phenomenon, adjusting the feeder line which has the reverse power transmission phenomenon and allows reverse power transmission to reduce the generated power so as to realize the adjustment of the reverse power transmission of the transformer station, and taking the reduced generated power as a final photovoltaic power generation scheduling plan. The method is realized based on an original power flow plan, the logic of reverse power transmission adjustment is simple and easy to realize, and stable operation of a power grid is ensured.

Description

Technical Field

[0001] The invention relates to a method and device for determining a distributed photovoltaic reverse power transmission dispatching plan, and belongs to the field of photovoltaic power generation dispatching plan. Background Art

[0002] At present, distributed photovoltaic power generation equipment has gradually become the mainstream of new energy power generation technology with its own advantages of low investment cost, long service life, no pollution and significant stability. After the distributed photovoltaic power generation is connected to the grid, when it reaches a certain limit, it will have a great impact on the operation quality, stability and safety of the grid. The three-phase imbalance of the distributed photovoltaic system is prone to reverse power transmission. The reverse power transmission phenomenon is that under certain circumstances, the electric energy generated in the distributed photovoltaic power generation system is reversely injected into the grid through the inverter to supply power to the grid. However, in the normal and stable operation of the grid, the reverse power transmission will cause the grid to operate unbalanced, causing voltage and frequency fluctuations, and thus affecting the stability and safety of electricity consumption. At the same time, the quality of the reverse power cannot meet the requirements of some electrical equipment, thereby causing interference and damage to the electrical equipment. The current scheduling plan only considers constraints such as line load rate, main transformer load rate, and node voltage limit. With supply and demand balance and economic operation as the optimization goals, the flow calculation is performed to finally generate the power generation plan value of each power generation unit. The scheduling plan will still have reverse power transmission during implementation, which will affect the safe and stable operation of the power grid. Summary of the invention

[0003] The purpose of the present invention is to provide a method and device for determining a distributed photovoltaic reverse power transmission scheduling plan, so as to solve the problem that reverse power transmission occurs in the existing scheduling plan, which in turn affects the stable and safe operation of the power grid.

[0004] To achieve the above object, the solution of the present invention includes:

[0005] A method for determining a distributed photovoltaic reverse power transmission scheduling plan of the present invention comprises the following steps:

[0006] Obtain the initial photovoltaic power generation scheduling plan results, and determine whether there is reverse power transmission in the feeder and each substation according to the load conditions in the calculated scheduling results. The feeder refers to the line used to connect the substation and the user side station area;

[0007] When only the feeder has reverse power transmission, the feeder that is not allowed to reverse power transmission is controlled to reduce the distributed generation power;

[0008] When reverse power transmission exists in both feeders and substations, the power generation capacity of the feeders that do not allow reverse power transmission is reduced. If reverse power transmission still exists in the current substation, the power generation capacity of the feeders that have reverse power transmission and allow reverse power transmission is reduced to achieve the regulation of reverse power transmission of the substation. The power generation capacity after reduction is used as the final photovoltaic power generation scheduling plan.

[0009] Beneficial effect: The photovoltaic power generation reverse power dispatching method of the present invention fully considers the reverse power transmission situation of the feeder and the substation in the process of forming the final dispatching plan. When the reverse power transmission phenomenon occurs in the feeder, the feeder that does not allow reverse power transmission is adjusted to reduce the power generation power, thereby eliminating the reverse power transmission phenomenon. When the reverse power transmission phenomenon exists in both the feeder and the substation, the power of the feeder that does not allow reverse power transmission is adjusted first. When the problem is still not solved, the feeder that allows reverse power transmission is adjusted to reduce the power generation power to achieve reverse power regulation. This method can effectively solve the reverse power transmission problem by adjusting the power of the feeder on the basis of the original dispatching plan. There is no need to recalculate the flow and modify the original plan. It is simple to implement and the adjustment speed is relatively fast. It can quickly adjust the reverse power transmission to ensure the safe and stable operation of the power grid.

[0010] Furthermore, when the reverse power transmission phenomenon still exists in the substation after the feeder that does not allow reverse power transmission is reduced in power generation, the adjustment method is as follows: determine the feeders with reverse power transmission phenomenon and the feeders that allow reverse power transmission whose load rate exceeds the set threshold, and reduce the power of the feeders whose load rate exceeds the set threshold until the reverse power transmission phenomenon in the substation disappears, or all feeders whose load rate exceeds the set threshold are adjusted to a load rate not greater than the set threshold.

[0011] Beneficial effect: By adjusting the power of feeders with or running reverse power transmission, the reverse power transmission of the substation can be adjusted. In this way, the power of feeders whose reverse power transmission load rate exceeds the set threshold can be adjusted, ensuring the stable operation of the power grid.

[0012] Furthermore, when the power of a feeder whose load factor exceeds a set threshold is reduced, the power is reduced in descending order of the absolute value of the load factor.

[0013] Beneficial effect: By adjusting the power of feeders with or without reverse power transmission, the reverse power transmission of the substation can be adjusted. The reverse power transmission of the substation can be quickly reduced in order of load rate, thereby ensuring the stable operation of the power grid.

[0014] Furthermore, when all feeders with load rates exceeding a set threshold are adjusted to a value not greater than the set threshold, if reverse power transmission still exists in the substation, all feeders with reverse power transmission are reduced so that the total power value of each reverse power feeder is equal to the remaining power value, and the remaining power value refers to the difference between the power value that needs to be adjusted by the substation and the total power value that has been adjusted for the feeder.

[0015] Beneficial effect: When all feeders are adjusted to a load rate not greater than a set threshold, if the substation still has reverse power transmission, all feeders with reverse power transmission will be reduced to eliminate the reverse power transmission phenomenon of the substation. If the requirements are still not met after adjustment, the present invention will continue to adjust by calculating the remaining power that needs to be adjusted, which is convenient for subsequent adjustments and will not cause a certain feeder to be continuously reduced, causing the power of the feeder to be too small after the reduction, thereby affecting the normal operation of power generation.

[0016] Furthermore, when adjusting all feeders with reverse power transmission, the power generation power of each feeder is reduced according to a set ratio, and the set ratio is obtained according to the remaining power value and the total power value of each feeder with reverse power transmission.

[0017] Beneficial effect: The power of all feeders with reverse power transmission is reduced in proportion. The adjustment method is relatively fair, avoiding uneven adjustment that affects the normal operation of the power grid and user-side stations.

[0018] Furthermore, when adjusting all feeders with reverse power transmission, the power that needs to be reduced for each feeder with reverse power transmission is determined according to the number of feeders with reverse power transmission, and each feeder with reverse power transmission performs equal power reduction according to the determined power.

[0019] Beneficial effect: The power of all feeders with reverse power transmission is reduced by an equal amount without a large amount of calculation. It is only necessary to know the number of feeders with reverse power transmission and distribute the remaining power to be adjusted evenly to each feeder to avoid affecting the normal operation of the power grid and user-side substations.

[0020] Furthermore, each substation and feeder is provided with a soft pressure plate, which is used to control the on and off of reverse power transmission.

[0021] A distributed photovoltaic reverse power transmission scheduling plan determination device of the present invention includes a processor, and the processor is used to execute instructions to implement the distributed photovoltaic power generation reverse power transmission scheduling determination method as described above.

[0022] Beneficial effects: The photovoltaic power generation reverse power transmission scheduling determination device of the present invention has a simple structure and includes a processor. The processor can better implement a distributed photovoltaic power generation reverse power transmission scheduling determination method. It does not require recalculation of the flow and modification of the original plan. It can quickly adjust the reverse power transmission to ensure safe and stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a process in an embodiment of the method of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0025] The idea of ​​the present invention is to provide a method for controlling reverse power transmission of distributed photovoltaic power generation on the basis of the original scheduling plan. The formulation of the scheduling plan usually takes the line load rate, main transformer load rate, node voltage limit and the like as constraints, takes supply and demand balance and economic operation as optimization goals, performs flow calculations, and finally generates the power generation plan value of each power generation unit. The scheduling plan of the present invention adds the constraint conditions for controlling reverse power transmission on the basis of the existing plan, and meets the demand for controlling reverse power transmission by adjusting the reverse power transmission on the feeder and the reverse power transmission of the substation.

[0026] Distributed photovoltaic reverse power transmission scheduling plan determination method embodiment:

[0027] like Figure 1 A distributed photovoltaic power generation reverse power control method shown in the figure first obtains the distributed photovoltaic power generation plan generated by the original strategy, and judges whether the feeder and each substation have reverse power transmission according to the results of the plan implementation. When only the feeder has reverse power transmission, the feeder that does not currently allow reverse power transmission is controlled to reduce the distributed power generation power; when both the feeder and the substation have reverse power transmission, the adjustment method when only the feeder has reverse power transmission is preferentially followed. If the substation still has reverse power transmission after adjustment, the feeder with reverse power transmission and allowed reverse power transmission is adjusted to reduce the power generation power to achieve the regulation of reverse power transmission of the substation. The following is a specific implementation method.

[0028] Obtain the initial photovoltaic power generation scheduling plan results, and determine whether there is reverse power transmission in the feeder and each substation based on the load conditions in the calculated scheduling results. The feeder refers to the line used to connect the substation and the user-side station area.

[0029] Specifically, it is necessary to first determine the system network framework, generate all distributed photovoltaic power generation plans according to the original strategy, and then divide the system network framework into regions according to the substation with the highest voltage level, wherein each region does not affect each other when adjusting the scheduling plan. Secondly, in this embodiment, each substation and feeder is provided with a soft pressure plate for controlling reverse power transmission. The soft pressure plate can also determine whether the feeder allows reverse power transmission. When the soft pressure plate is displayed as "true", reverse power transmission is allowed; when the soft pressure plate is "false", reverse power transmission is not allowed.

[0030] According to the execution results of the distributed photovoltaic power generation dispatch plan, it is judged whether each feeder and each substation has reverse power transmission. The judgment basis for feeder reverse power transmission is whether the load rate of the feeder is negative. When the load rate of the feeder is negative, it means that the feeder has reverse power transmission, otherwise it does not exist.

[0031] When only the feeder has reverse power transmission, the feeder that is not allowed to reverse power is controlled to reduce the distributed power generation power; when both the feeder and the substation have reverse power transmission, the power generation power of the feeder that is not allowed to reverse power is reduced. If the substation still has reverse power transmission, the feeder that has reverse power transmission and allows reverse power is adjusted to reduce (adjust and reduce) the power generation power to achieve the regulation of reverse power transmission of the substation.

[0032] Specifically, when there is reverse power transmission only on the feeder, the reverse power value is S L . Query the reverse power soft pressure plate corresponding to the reverse power feeder. If the soft pressure plate is "true", that is, reverse power is allowed, no processing is performed. If the soft pressure plate is "false", control the feeder to reduce the distributed generation power, and the adjusted power value is S L . This embodiment determines whether the feeder and substation are allowed to reverse power according to the provisions of the "Guidelines for Assessment of the Carrying Capacity of Distributed Generation Access to the Grid" (DL / T 2041-2019). By default, substations above 220kV are not allowed to reverse power, and substations with unidirectional power supply design (substations are connected to substations through feeders) or substations are not allowed to reverse power, such as some substations or substations with special loads such as hospitals and schools. Substations designed for unidirectional power supply are not allowed to reverse power. If reverse power is required, the system needs to be modified. Most of the substations below 220220kV allow reverse power. Whether substations and substations are allowed to reverse power can be modified according to actual conditions, but in actual situations, there will generally be no frequent changes.

[0033] When there is reverse power transmission in both the feeder and the substation, obtain the reverse power S of the substation s First, if the soft pressure plate corresponding to the feeder shows "false", the feeder with reverse power transmission and the feeder that does not allow reverse power transmission is controlled to reduce the distributed generation power. The power value adjusted by the feeder is recorded as:

[0034]

[0035] The power value of feeder regulation and the reverse power S of substation s Compare, if it satisfies:

[0036]

[0037] This means that the reverse power problem can be solved by reducing the power of the feeders that have reverse power transmission and are not allowed. Otherwise, it means that the reverse power transmission of the feeder has been solved, but the problem of reverse power transmission in the substation still exists, and it is necessary to continue to adjust the distributed generation power of the feeder. The adjustment method is: determine the feeders with load rates exceeding the set threshold among the feeders that have reverse power transmission and are allowed to reverse power, and reduce the power of the feeders with load rates exceeding the set threshold until the reverse power transmission of the substation disappears, or all feeders with load rates exceeding the set threshold are adjusted to a load rate not greater than the set threshold. Among them, in order to increase the adjustment rate, when this embodiment reduces the power of the feeder with a load rate exceeding the set threshold, it is reduced in order from large to small in the order of the absolute value of the load rate. Specifically, when there is reverse power transmission in the substation, the absolute values ​​of the load rates of the feeders that have reverse power transmission and allow reverse power transmission are sorted. When the maximum load rate of the feeders that have reverse power transmission and allow reverse power transmission exceeds the set threshold, the feeder corresponding to the maximum load rate is reduced in power generation until the power value after the reduction is no greater than the set threshold. At this time, if there is still reverse power transmission in the substation, the feeders that have reverse power transmission and allow reverse power transmission that exceed the set threshold are selected in order of load rate and are reduced until the reverse power transmission in the substation no longer exists, or all feeders whose load rates exceed the set threshold are adjusted to have a load rate no greater than the set threshold.

[0038] Specifically, if the maximum load factor exceeds a set threshold (eg, 80%), the power of the feeder corresponding to the maximum load factor is reduced to reduce the load factor to the set threshold. L-1 . Determine whether the power values ​​adjusted twice are greater than the reverse power of the substation, that is:

[0039]

[0040] If the inequality holds, the adjustment is complete, and both the feeder reverse power transmission and the substation reverse power transmission problems can be solved. If the inequality does not hold, the power of the corresponding feeders whose load rates exceed the set threshold will continue to be adjusted in the order of load rates. This is done until the power values ​​adjusted for multiple feeders satisfy the following inequality:

[0041]

[0042] If the inequality holds, the adjustment ends. If the inequality still does not hold, the adjustment continues until the load rate of all reverse power feeders is no greater than the set threshold. When all feeders with load rates exceeding the set threshold are adjusted to no greater than the set threshold, if the substation still has reverse power transmission, all feeders with reverse power transmission are reduced so that the total power reduction of each reverse power feeder is equal to the residual power value, where the residual power value refers to the difference between the power value that the substation needs to adjust and the total power value that the feeder has adjusted. The residual power value that needs to be adjusted is S s-1 for:

[0043]

[0044] This embodiment provides two adjustment methods, one of which is proportional adjustment: that is, when adjusting all feeders with reverse power transmission, the power generation power of each feeder is reduced according to a set ratio, and the set ratio r is obtained according to the remaining power value and the total power value of each feeder with reverse power transmission. The ratio r that needs to be adjusted for each reverse power feeder is:

[0045]

[0046] In the formula, S s-1 is the power value that still needs to be adjusted after the feeder that allows reverse power transmission is adjusted, r is the ratio of each reverse power feeder that needs to be adjusted, S L ′ i is the reverse power corresponding to each feeder. If r = 3.21%, each feeder will adjust the reverse power value to the original 1-3.21% = 96.79%. The original reverse power of a feeder is 100kW. After adjustment, the reverse power value is 96.79kW. After all reverse feeders are adjusted, the reduced power generation is used as the final photovoltaic power generation scheduling plan.

[0047] The second is an equal power adjustment method: that is, when adjusting all feeders with reverse power transmission, the power that needs to be reduced for each feeder with reverse power transmission is determined according to the number of feeders with reverse power transmission, and each feeder with reverse power transmission is reduced according to the determined power. Specifically, first, the power that needs to be reduced for each feeder with reverse power transmission is determined by the ratio between the residual power value that needs to be adjusted and the number of feeders with reverse power transmission, and each feeder with reverse power transmission is adjusted to equal power according to the calculated power reduction. This embodiment only provides two adjustment methods. As other implementation methods, it is sufficient as long as the total power reduction value of each feeder with reverse power transmission satisfies the residual power value that needs to be adjusted.

[0048] In summary of the above process, when reverse power transmission occurs in the feeder, the feeder that does not allow reverse power transmission is controlled to adjust and reduce the power generation, thereby eliminating the reverse power transmission phenomenon. When reverse power transmission occurs in both the feeder and the substation, the power of the feeder that does not allow reverse power transmission is adjusted first. When the problem is not solved, the feeder that allows reverse power transmission is adjusted to reduce the power generation to achieve reverse power regulation. This method can effectively solve the reverse power transmission problem by adjusting the power of the feeder on the basis of the original dispatch plan. It does not require recalculation of the flow or modification of the original plan. It is simple to implement and the adjustment speed is relatively fast. It can quickly adjust the reverse power transmission to ensure the safe and stable operation of the power grid.

[0049] Distributed photovoltaic reverse power transmission dispatch plan determination device embodiment:

[0050] A distributed photovoltaic power generation reverse power transmission scheduling determination device in this embodiment includes a memory, a processor, and an internal bus. The processor and the memory complete mutual communication and data interaction through the internal bus. The memory includes at least one memory capable of storing the power and load rate of each substation and feeder, as well as the soft pressure plate data set for each substation and feeder. The processor executes various functional applications and data processing by running software programs and modules stored in the memory, and implements the distributed photovoltaic power generation reverse power transmission scheduling determination method introduced in the method embodiment of the present invention.

[0051] That is to say, the methods in the above method embodiments should be understood as processes for implementing the distributed photovoltaic power generation reverse power transmission scheduling determination method that can be realized by computer program instructions. These computer program instructions can be provided to the processor, so that the functions specified in the above method processes are generated by the processor executing these instructions.

[0052] Among them, the processor can be a processing device such as a microprocessor MCU or a field programmable gate array FPGA.

[0053] The memory can be various memories that store information in the form of electrical energy, such as RAM, ROM, etc.; it can also be various memories that store information in the form of magnetic energy, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, bubble memories, USB flash drives, etc.; it can also be various memories that store information in the form of optical energy, such as CDs, DVDs, etc.; of course, it can also be other types of memories, such as quantum memories, graphene memories, etc.

[0054] The specific implementation manners are given above, but the present invention is not limited to the described implementation manners. The basic idea of the present invention lies in the above basic solution. For those of ordinary skill in the art, according to the teachings of the present invention, it does not require creative labor to design various deformed models, formulas, and parameters. Changes, modifications, substitutions, and variations made to the implementation manners without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for determining a distributed photovoltaic reverse power transmission scheduling plan, It is characterized in that The following steps are involved: Obtain the initial photovoltaic power generation scheduling plan results, and determine whether there is reverse power transmission in the feeder and each substation according to the load conditions in the calculated scheduling results. The feeder refers to the line used to connect the substation and the user side station area; When only the feeder has reverse power transmission, the power generation of the feeder that does not allow reverse power transmission is reduced; When reverse power transmission exists in both feeders and substations, the power generation capacity of feeders that do not allow reverse power transmission is reduced. If reverse power transmission still exists in the current substation, the power generation capacity of feeders that have reverse power transmission and allow reverse power transmission is reduced to achieve the regulation of reverse power transmission of the substation. The power generation capacity after reduction is used as the final photovoltaic power generation scheduling plan.

2. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 1, It is characterized in that When the reverse power transmission phenomenon still exists in the substation after the feeders that are not allowed to reverse power transmission are reduced in power generation, the adjustment method is as follows: determine the existence of reverse power transmission phenomenon and among the feeders that are allowed to reverse power transmission, the feeders whose load rate exceeds the set threshold are reduced in power until the reverse power transmission phenomenon in the substation disappears, or all feeders whose load rate exceeds the set threshold are adjusted to a load rate not greater than the set threshold.

3. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 2, It is characterized in that When reducing the power of a feeder whose load factor exceeds the set threshold, the power is reduced in descending order according to the absolute value of the load factor.

4. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 2, It is characterized in that When all feeders with load rates exceeding the set threshold are adjusted to not greater than the set threshold, if reverse power transmission still exists in the substation, all feeders with reverse power transmission will be reduced so that the total power reduced by each feeder with reverse power transmission is equal to the remaining power value, which refers to the difference between the power value that needs to be adjusted by the substation and the total power value that has been adjusted for the feeder.

5. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 4, It is characterized in that When adjusting all feeders with reverse power transmission, the power generation power of each feeder is reduced according to a set ratio, and the set ratio is obtained according to the remaining power value and the total power value of each feeder with reverse power transmission.

6. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 4, It is characterized in that When adjusting all feeders with reverse power transmission, the power that needs to be reduced for each feeder with reverse power transmission is determined according to the number of feeders with reverse power transmission, and each feeder with reverse power transmission performs an equal power reduction according to the determined power.

7. The method for determining a distributed photovoltaic reverse power transmission scheduling plan according to claim 1, It is characterized in that Each substation and feeder is provided with a soft pressure plate, which is used to control the on and off of reverse power transmission.

8. A distributed photovoltaic reverse power transmission scheduling plan determination device, comprising a processor, It is characterized in that The processor is used to execute instructions to implement the distributed photovoltaic power generation reverse power transmission scheduling determination method as described in any one of claims 1 to 7.

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