Large-scale distributed photovoltaic power grid low-voltage load shedding method and system

Abstract

The invention belongs to the technical field of power systems, and discloses a large-scale distributed photovoltaic power grid low-voltage load shedding method and system, and the method comprises the steps: taking the sensitivity degree of load shedding change for node voltage control as an index, selecting a low-voltage load shedding power distribution network region, analyzing the importance of load branches in the region, and obtaining a comprehensive influence index, determining a load branch needing to be cut off in the power distribution network area based on the comprehensive influence index; the low-voltage load shedding amount is calculated in a reactive voltage sensitivity mode, and the comprehensive load shedding amount is calculated by considering reactive support provided by large-scale distributed photovoltaic in the voltage drop period; and improving the action condition of low-voltage load shedding by considering the standard of distributed photovoltaic low-voltage ride-through to obtain a power grid low-voltage load shedding strategy. According to the method, the load shedding position, the load shedding amount, the action voltage and the load shedding delay of low-voltage load shedding are improved respectively, and the improved low-voltage load shedding strategy is more suitable for solving the voltage stability problem under the future distributed photovoltaic development.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a low-voltage load reduction method and system for a power grid containing large-scale distributed photovoltaics. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As one of the main ways to utilize new energy, large-scale distributed photovoltaic power generation has developed rapidly in the receiving power grids in central and eastern my country. However, the current matching between distributed photovoltaic power generation and low-voltage load reduction control of the power grid is poor, and the large-scale distributed photovoltaic power generation has brought new challenges to the safe and stable operation of the power grid.

[0004] When an accident occurs in the power system, the low-voltage load shedding device is used to restore the entire system to normal as soon as possible. When the voltage drops due to reactive power shortage in the power system, the low-voltage load shedding device will automatically cut off part of the power user's load in turns according to the voltage reduction value, so that the power supply and load of the system are rebalanced, preventing voltage collapse accidents and restoring the entire system to normal as soon as possible.

[0005] Low-voltage load shedding mainly includes load shedding location, load shedding amount, action voltage, action delay, etc. The traditional low-voltage load shedding control strategy does not take into account the new scenario of large-scale distributed photovoltaic grid connection. Therefore, the application of traditional low-voltage load shedding control strategy in the new scenario will cause a series of problems: the selection of traditional low-voltage load shedding locations will cause a large number of distributed photovoltaic units to be cut off; the setting of traditional load shedding amount, action delay, and action voltage does not take into account the requirements of low-voltage ride-through for photovoltaic grid connection. Load shedding that does not meet the requirements of low-voltage ride-through may cause large-scale distributed grid disconnection; distributed photovoltaic grid connection will also reduce the load demand for power on the grid, resulting in a decrease in net load shedding, making the voltage recovery effect unsatisfactory, etc. If a large-scale photovoltaic grid-connected power generation system is disconnected from the grid, the active and reactive power of the entire system will undergo tremendous changes, resulting in a sharp drop in the frequency and voltage of the grid and an expansion of the fault range. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a low-voltage load shedding method and system for a power grid containing large-scale distributed photovoltaics, and improves the load shedding position, load shedding amount, action voltage and action delay of low-voltage load shedding. The improved low-voltage load shedding strategy is more suitable for solving the voltage stability problem under the future development of distributed photovoltaics.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for reducing load in a power grid with low voltage including large-scale distributed photovoltaic power generation, comprising the following steps: Taking the sensitivity of load shedding to node voltage control as an indicator, the distribution network area for low-voltage load shedding is selected, the importance of the load branches in the distribution network area is analyzed, and the comprehensive impact index is obtained. Based on the comprehensive impact index, the load branches that need to be cut off in the distribution network area are determined; The reactive voltage sensitivity method is used to calculate the low-voltage load reduction, and the reactive support provided by large-scale distributed photovoltaics during voltage drops is considered to calculate the comprehensive load reduction; Considering the standard of low voltage ride-through of distributed photovoltaics, the action conditions of low voltage load shedding are improved, and the low voltage load shedding strategy of the power grid containing large-scale distributed photovoltaics is obtained.

[0008] As an optional implementation, the comprehensive impact index is obtained by comprehensively evaluating the low voltage severity index, the branch power proportion index, the load shedding economic loss index and the load branch sensitivity index.

[0009] As an optional implementation, the action condition includes an action voltage and an action delay.

[0010] As an optional implementation method, the action delay is improved, the low voltage ride-through requirements of distributed photovoltaics are considered, and the action delay is optimized using the dynamic delay parameters of the recovery process, specifically: The first round of action delay requirements meet: < <Set time; The delay requirements for subsequent rounds of actions must meet the following requirements:

[0011] in, The time set to avoid malfunction of the load shedding device. For the i -1 ( i ≥2) After the load shedding action, the voltage is still lower than the first i The moment of wheel action voltage, For the i Wheel action delay, For the i Wheel action voltage, is the real-time voltage, and C is a constant.

[0012] As an optional implementation, the action voltage is improved as follows: The voltage of the first round is set to the first threshold, the voltage of the last round is set to be higher than the second threshold, and the other rounds are evenly distributed between the second threshold and the first threshold.

[0013] As an optional implementation, the comprehensive impact index is calculated by entropy weight method, specifically:

[0014] Among them, S1 is the low voltage severity index, S2 is the branch power ratio index, S3 is the load branch sensitivity, and S4 is the load shedding economic loss. , , , Respectively represent , , , The weight size.

[0015] In a second aspect, the present invention provides a low-voltage load reduction system for a power grid including large-scale distributed photovoltaics, comprising: The load shedding location selection module is configured to: select the distribution network area for low-voltage load shedding based on the sensitivity of load shedding to node voltage control, analyze the importance of load branches in the distribution network area, obtain comprehensive impact indicators, and determine the load branches that need to be cut off in the distribution network area based on the comprehensive impact indicators; The load reduction calculation module is configured to: calculate the low voltage load reduction by using reactive voltage sensitivity, consider the reactive support provided by the large-scale distributed photovoltaic during the voltage drop period, and calculate the comprehensive load reduction; The action condition setting module is configured to: consider the standard of distributed photovoltaic low voltage ride-through, improve the action conditions of low voltage load reduction, and obtain the low voltage load reduction strategy of the power grid containing large-scale distributed photovoltaic.

[0016] In a third aspect, the present invention provides an electronic device comprising a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in the first aspect is performed.

[0017] In a fourth aspect, the present invention provides a computer-readable storage medium for storing computer instructions, wherein when the computer instructions are executed by a processor, the method described in the first aspect is performed.

[0018] In a fifth aspect, the present invention provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method described in the first aspect.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present disclosure proposes a low-voltage load shedding method and system for a power grid containing large-scale distributed photovoltaics. The implementation of low-voltage load shedding requires selecting a suitable low-voltage load shedding position. The method of screening the load shedding branch in two stages can reduce the load shedding amount while reducing the loss of distributed photovoltaic units during load shedding, which is conducive to reducing the economic loss of load shedding and supporting voltage stability. The recovery after the voltage drop often requires the removal of a certain amount of load. The present disclosure takes into account the problem of insufficient low-voltage load shedding in new scenarios. Combined with the reactive support capacity of distributed photovoltaics, the calculated load shedding meets the requirements of voltage recovery in new scenarios, which helps to improve the voltage recovery capacity. The action voltage and action delay constitute the action conditions of low-voltage load shedding. After the voltage is lower than the action voltage and the duration meets the action delay, the low-voltage load shedding device acts. Combined with the requirements of low voltage ride-through, the reasonable setting of the action voltage and dynamic action delay can meet the voltage recovery requirements in the large-scale distributed photovoltaic grid-connected scenario. The improvement of the action conditions considering the requirements of low voltage ride-through can avoid the disconnection of large-scale distributed photovoltaic units from the grid, avoid the reduction of the voltage and frequency of the power system, reduce the impact of photovoltaic disconnection on the stability of the power system, and is conducive to voltage stability.

[0020] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 This is the voltage recovery diagram after low voltage load shedding; Figure 2 Low voltage ride-through standard for photovoltaic grid connection; Figure 3 A framework diagram of a low-voltage load reduction method for a power grid containing large-scale distributed photovoltaics provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "include" and "have" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0027] Explanation of terms Low-voltage load shedding: When the voltage drops due to reactive power shortage in the power system, the low-voltage load shedding device will automatically cut off part of the power user's load according to the voltage reduction value, so as to rebalance the power supply and load of the system, prevent voltage collapse accidents, and restore the entire system to normal as soon as possible.

[0028] Example 1 like Figure 3 As shown, this embodiment provides a method for reducing load on a power grid with low voltage including large-scale distributed photovoltaic power generation, comprising the following steps: S1. Taking the sensitivity of load shedding to node voltage control as an indicator, select the distribution network area for low-voltage load shedding, analyze the importance of the load branches in the distribution network area, obtain the comprehensive impact index, and determine the load branches that need to be cut off in the distribution network area based on the comprehensive impact index; S2. Calculate the low-voltage load reduction by using reactive voltage sensitivity, taking into account the reactive support provided by large-scale distributed photovoltaics during voltage drops, and calculate the comprehensive load reduction; S3. Considering the standard of low voltage ride-through of distributed photovoltaics, the operating conditions of low voltage load reduction are improved to obtain the low voltage load reduction strategy of the power grid containing large-scale distributed photovoltaics.

[0029] The first is the selection of the load reduction position.

[0030] The present disclosure uses a two-stage target screening method to optimize the low-voltage load shedding site selection. In the first stage, because different distribution network areas have different effects on the target bus voltage, the distribution network areas that have a stronger effect on the low-voltage bus voltage recovery (that is, the distribution network under the higher voltage level bus) are given priority for load shedding. Secondly, the action of the low-voltage load shedding device of the load branch in each distribution network area should not only consider the load loss of the system under uncertain faults, but also the impact of the load branch containing distributed photovoltaics after removal. The present disclosure uses the comprehensive impact index as an indicator, that is, to determine the specific load shedding branch with the purpose of minimizing the comprehensive impact after the load branch is removed, which is the second stage.

[0031] Step 1): Using the analytical sensitivity of load shedding to node voltage control as an indicator, select the appropriate distribution network area to select the load shedding branch. In this way, when the same size of load is removed, the voltage in the area with high sensitivity recovers better, while reducing resource waste.

[0032] For any power grid containing distributed photovoltaics, according to Kirchhoff's law, the following node voltage equation can be written: (1) Where: and are the voltage and current phasors of the load nodes respectively; The current phasor generated by the distributed photovoltaic included in the load branch; is the voltage phasor of the generator node; and are the number of generator nodes and the number of load nodes respectively; is the system network impedance matrix facing the load node; The relationship matrix between the load node voltage vector and the generator node voltage vector when all load branches are open.

[0033] Further arrangement can be obtained as follows: (2) Where: is the voltage amplitude; and Power output for loads and distributed photovoltaics; is the phase angle of each phase quantity; is the load power factor.

[0034] The key parameters extracted from formula (2) are as follows: (3) (4) and Respectively represent nodes k Effects of load shedding and PV output changes on nodes i By comparing and By measuring the size of the load shedding, the area of ​​the distribution network most suitable for load shedding can be determined to improve the voltage at the low-voltage node.

[0035] Step 2): After determining the distribution network area for load shedding, it is necessary to determine the specific load branches in the area. Qualitative analysis is performed on the importance of load branches, and multiple indicators such as low voltage severity index, branch power ratio index, load shedding economic loss index, and load branch sensitivity index are comprehensively evaluated through the entropy weight method to obtain the comprehensive impact index of load branch removal. In specific scenarios, the comprehensive impact index is compared to determine the appropriate load branch removal combination, and the schemes of multiple typical application scenarios are compared and analyzed to determine the comprehensive load branch removal scheme suitable for multiple scenarios.

[0036] The specific contents of the above indicators are as follows: ① Low voltage severity index: Shedding load at nodes with lower voltage helps improve node voltage. The more severe the voltage drop is, the greater the need for load shedding.

[0037] (5) In the formula, The minimum value of the allowable voltage deviation, please refer to the "Technical Guidelines for Voltage and Reactive Power in Power Systems"; Represents the load node voltage.

[0038] ② Branch power ratio index: The higher the index is, the lower the distributed photovoltaic output of the load branch is. A value of 0 means that the photovoltaic power generation of the branch is sufficient to support the load demand and there is no need to remove the branch.

[0039] (6) in, Represents photovoltaic output, Represents load demand.

[0040] ③ Load branch sensitivity: Considering the different effects of different types of loads on voltage changes. The more constant power loads and induction motor loads there are in the branch load, the more beneficial it is to voltage recovery to cut off the load branch, and it is more suitable as a load shedding branch.

[0041] (7) in: Indicates the induction motor load; represents constant power load; Represents the total branch load ④ Economic loss of load shedding (8) in, i ( i =1...n) indicates the branch load classification; Represents the corresponding size of different loads; represents the unit load loss cost; Represents the loss of distributed photovoltaic units.

[0042] The above indicators are comprehensively evaluated, and the indicators are calculated by simulation data and entropy weight method. The total comprehensive impact indicators are as follows: (9) Among them: S1 is the low voltage severity index, S2 is the branch power proportion index, S3 is the load branch sensitivity, and S4 is the load shedding economic loss. , , , Respectively represent , , , The weight size.

[0043] According to the final comprehensive impact index, specific load shedding branches are selected from large to small to form a specific plan. Different typical scenarios may form different plans, and the load shedding branches that are selected the most times can be combined as a load shedding branch plan applicable to all scenarios.

[0044] Calculation of load reduction.

[0045] The present disclosure adopts the reactive power-voltage sensitivity method to calculate the low-voltage load reduction. Considering that large-scale distributed photovoltaics will provide a large amount of reactive power to support voltage stability during voltage drops, the comprehensive load reduction is calculated based on this.

[0046] Step 1): If the action voltage of each round of bus k is known (i=1,2,3,...,n represents the total number of rounds of action), a reactive-voltage sensitivity coefficient can be calculated for each round of action voltage, so that the relationship between the reactive power and voltage of the bus can be more accurately expressed. The calculation formula of the reactive-voltage regulation effect coefficient of bus k load can be obtained by the method described above: (10) Where: For bus k Voltage is Reactive power-voltage sensitivity coefficient at ; and The bus voltage is The reactive power change and voltage change at that time; , , Busbar k The reactive power and voltage at the target recovery voltage are Reactive power and target recovery voltage at that time.

[0047] Since the initial reactive power of each busbar is very different, the calculated There is also a big difference. The data alone cannot reflect the voltage stability and needs to be processed in a certain way.

[0048] Define sensitivity as: (11) Where: Eliminating the influence caused by the difference in initial reactive power, The influence of different initial voltages is eliminated. By observing the sensitivity, the voltage stability of each node can be clearly understood.

[0049] After calculating the sensitivity, the load reduction in each round is as follows: (12) in, Indicates i The per unit value of wheel load reduction; Before i -1 round of load shedding total per unit value.

[0050] Step 2): In a power system containing large-scale distributed photovoltaics, since the distributed photovoltaic inverter will enter the low voltage ride-through state from the normal operation state when the voltage drops, the photovoltaic inverter will provide reactive support to reduce the voltage drop, thereby slowing down the voltage decay and reducing the possibility of voltage collapse.

[0051] according to Figure 1 This shows the defects of load shedding calculation in power systems with distributed photovoltaic pairs. The target recovery voltage after a fault is set to 0.9pu. In a power grid without distributed photovoltaics, the bus voltage at a certain point drops to a voltage of After the load reduction After the load is restored to 0.9pu, its change curve is , when the bus voltage drops to After the load reduction After the load is restored to 0.9pu, its change curve is ,because , so the required load reduction When in a grid with a large number of distributed photovoltaics, the voltage should drop to The reactive power shortage can only cause the voltage to drop to The theoretical load reduction is , during the voltage recovery process, the reactive power support provided by the inverter will decrease, so the required load reduction is greater than , and eventually can only recover to , and its variation curve is .

[0052] The expression of the percentage of reactive current required during low voltage ride-through is shown in equation (13).

[0053] (13) The missing reactive power can be regarded as the reactive support of distributed photovoltaics that has not been removed during low-voltage load shedding when the voltage drops. The specific reactive output can refer to formula (13). The output current is the reactive current, and the reactive support at this time can be calculated based on this: (14) Then the per unit value of each round of load reduction is: (15) in, It is the per unit value of the total load shedding in each round.

[0054] Action condition setting.

[0055] The action conditions include action voltage and action delay. Considering the standards for low voltage ride-through of distributed photovoltaics, the action voltage and action delay are improved respectively.

[0056] 1) Action voltage improvement: Considering the requirements of low voltage ride-through, when the voltage at the photovoltaic grid-connected point is lower than 0.9 pu, it can only be kept without disconnection for 2s at most. If it exceeds 2s, the photovoltaic grid will be disconnected, which will cause serious damage to the grid voltage. Therefore, when the voltage is lower than 0.9 pu, low voltage load reduction should be activated, so the first round is set to 0.9 pu; considering the provisions of the "Guidelines for Safety and Stability of Power Systems", the voltage of the last round should be higher than 0.8 pu, and the other rounds should be evenly distributed between 0.8 and 0.9 pu.

[0057] 2) Action delay improvement: Considering the low voltage ride-through requirements of distributed photovoltaics, the dynamic delay parameters of the recovery process are used to optimize the action delay. The specific method is as follows: ① The first round of action delay requirements meet: < <0.625s, where The time set to avoid false operation of the load shedding device.

[0058] ② The delay requirements for each subsequent round of actions are as follows: (16) in, For the i -1 ( i ≥2) After the load shedding action, the voltage is still lower than the first i The moment of wheel action voltage, For the i Wheel action delay, For the i Wheel action voltage, is the real-time voltage, and C is a constant.

[0059] when Less than threshold And last for a period of time , then start the low voltage load shedding. When C is determined, a larger voltage drop will shorten the time delay and the low voltage load shedding device will start quickly; when the voltage drop is small, the start delay of the low voltage load shedding device is relatively long.

[0060] Since the low voltage ride-through standard has time requirements, in order to avoid near lead to The value is very small, resulting in Exceeds the low penetration requirement, so when calculating the action delay, replace Replaced with the set target recovery voltage This fixed value. No matter how big it is, it will avoid Too small to cause Too large to meet the Figure 2 The photovoltaic low voltage ride through standard is shown.

[0061] Considering that the second half of the photovoltaic low voltage ride-through standard changes linearly, the selection of constant C should not cause delay in any case. Exceeds low wear requirements.

[0062] The present disclosure aims at a power system including large-scale distributed photovoltaics, and improves the load shedding position, load shedding amount, and action conditions to form a low-voltage load shedding strategy including large-scale distributed photovoltaics and configure a low-voltage load shedding scheme including large-scale distributed photovoltaics. When a power grid failure occurs, after the voltage drop at the monitoring point meets the low-voltage load shedding action conditions, the low-voltage load shedding is started, and the load is removed in turns until the voltage at the monitoring point returns to stability.

[0063] Example 2 This embodiment provides a low-voltage load reduction system for a power grid including large-scale distributed photovoltaics, including: The load shedding location selection module is configured to: select the distribution network area for low-voltage load shedding based on the sensitivity of load shedding to node voltage control, analyze the importance of load branches in the distribution network area, obtain comprehensive impact indicators, and determine the load branches that need to be cut off in the distribution network area based on the comprehensive impact indicators; The load reduction calculation module is configured to: calculate the low voltage load reduction by using reactive voltage sensitivity, consider the reactive support provided by the large-scale distributed photovoltaic during the voltage drop period, and calculate the comprehensive load reduction; The action condition setting module is configured to: consider the standard of distributed photovoltaic low voltage ride-through, improve the action conditions of low voltage load reduction, and obtain the low voltage load reduction strategy of the power grid containing large-scale distributed photovoltaic.

[0064] It should be noted that the above modules correspond to the steps described in Example 1, and the examples and application scenarios implemented by the above modules and the corresponding steps are the same, but are not limited to the contents disclosed in the above Example 1. It should be noted that the above modules, as part of the system, can be executed in a computer system such as a set of computer executable instructions.

[0065] In further embodiments, there is also provided: An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in Embodiment 1 is performed. For the sake of brevity, it will not be described in detail here.

[0066] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0067] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0068] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the method described in Example 1 is completed.

[0069] The method in Example 1 can be directly embodied as a hardware processor, or a combination of hardware and software modules in the processor. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware. To avoid repetition, it is not described in detail here.

[0070] A computer program product includes a computer program, and when the computer program is executed by a processor, the method described in embodiment 1 is implemented.

[0071] The present invention also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a real or virtual processor of the target to perform the process / method as described above. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or divided between program modules as needed. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0072] The computer program code for implementing the method of the present invention can be written in one or more programming languages. These computer program codes can be provided to the processor of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the computer or other programmable data processing device, causes the function / operation specified in the flow chart and / or block diagram to be implemented. The program code can be executed completely on a computer, partially on a computer, as an independent software package, partially on a computer and partially on a remote computer or completely on a remote computer or server.

[0073] In the context of the present invention, computer program codes or related data may be carried by any appropriate carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like. Examples of signals may include electrical, optical, radio, acoustic or other forms of propagation signals, such as carrier waves, infrared signals, and the like.

[0074] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with this embodiment can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0075] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for reducing load on a power grid with large-scale distributed photovoltaic power generation, characterized in that: The following steps are involved: Taking the sensitivity of load shedding to node voltage control as an indicator, the distribution network area for low-voltage load shedding is selected, the importance of the load branches in the distribution network area is analyzed, and the comprehensive impact index is obtained. Based on the comprehensive impact index, the load branches that need to be cut off in the distribution network area are determined; The reactive voltage sensitivity method is used to calculate the low-voltage load reduction, and the reactive support provided by large-scale distributed photovoltaics during voltage drops is considered to calculate the comprehensive load reduction; Considering the standard of low voltage ride-through of distributed photovoltaics, the action conditions of low voltage load shedding are improved, and the low voltage load shedding strategy of the power grid containing large-scale distributed photovoltaics is obtained.

2. A method for reducing load in a power grid with low voltage and large-scale distributed photovoltaic power generation as claimed in claim 1, characterized in that: The comprehensive impact index is obtained by comprehensively evaluating the low voltage severity index, the branch power proportion index, the load shedding economic loss index and the load branch sensitivity index.

3. A method for reducing load in a power grid with low voltage and large-scale distributed photovoltaic power generation as claimed in claim 1, characterized in that: The action conditions include an action voltage and an action delay.

4. A method for reducing load in a power grid with low voltage and large-scale distributed photovoltaic power generation as claimed in claim 3, characterized in that: The action delay is improved, the low voltage ride-through requirements of distributed photovoltaics are considered, and the action delay is optimized using the dynamic delay parameters of the recovery process. Specifically: The first round of action delay requirements meet: < <Set time; The delay requirements for subsequent rounds of actions must meet the following requirements: in, The time set to avoid false operation of the load shedding device. It is the moment when the voltage after the i-1th (i≥2)th round of load shedding action is still lower than the i-th round action voltage. is the delay of the i-th round of action, is the i-th round action voltage, is the real-time voltage, and C is a constant.

5. A method for reducing load in a power grid with low voltage and large-scale distributed photovoltaic power generation as claimed in claim 3, characterized in that: The specific improvements to the operating voltage are: The voltage of the first round is set to the first threshold, the voltage of the last round is set to be higher than the second threshold, and the other rounds are evenly distributed between the second threshold and the first threshold.

6. A method for reducing load in a power grid with low voltage and large-scale distributed photovoltaic power generation as claimed in claim 2, characterized in that: The comprehensive impact index is calculated by the entropy weight method, specifically: Among them, S1 is the low voltage severity index, S2 is the branch power ratio index, S3 is the load branch sensitivity, and S4 is the load shedding economic loss. , , , Respectively represent , , , The weight size.

7. A low-voltage load reduction system for a power grid containing large-scale distributed photovoltaics, characterized in that: include: The load shedding location selection module is configured to: select the distribution network area for low-voltage load shedding based on the sensitivity of load shedding to node voltage control, analyze the importance of load branches in the distribution network area, obtain comprehensive impact indicators, and determine the load branches that need to be cut off in the distribution network area based on the comprehensive impact indicators; The load reduction calculation module is configured to: calculate the low voltage load reduction by using reactive voltage sensitivity, consider the reactive support provided by the large-scale distributed photovoltaic during the voltage drop period, and calculate the comprehensive load reduction; The action condition setting module is configured to: consider the standard of distributed photovoltaic low voltage ride-through, improve the action conditions of low voltage load reduction, and obtain the low voltage load reduction strategy of the power grid containing large-scale distributed photovoltaic.

8. An electronic device, characterized in that: The method comprises a memory and a processor and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method according to any one of claims 1 to 6 is completed.

9. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the method described in any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises a computer program, which, when executed by a processor, implements the method according to any one of claims 1 to 6.

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