Evaluation method for distributed photovoltaic access power distribution network and related device

Abstract

The invention relates to the technical field of power system planning, in particular to an evaluation method for distributed photovoltaic access to a power distribution network and a related device. Acquiring feature data of a target power grid; according to the characteristic data, a power grid steady-state model and a power grid dynamic model are constructed, and the power grid steady-state model and the power grid dynamic model are coupled through a topological relation between nodes and branches; setting a photovoltaic access scene, performing load flow calculation in the photovoltaic access scene based on the power grid steady-state model to obtain a load flow calculation result of the power grid, and identifying a voltage out-of-limit region and a line overload risk point of the power grid according to the load flow calculation result; according to the method, through integrating geographic information, line parameters, transformer substation capacity, transformer transformation ratio and other multi-dimensional data, a steady-state and dynamic coupled power grid model is constructed, and the defect that a traditional single model cannot represent the coupling relation between photovoltaic dynamic characteristics and power grid inertia is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of power system planning, and in particular to an evaluation method and related devices for accessing a distributed photovoltaic power distribution network. Background Art

[0002] With the large-scale development of renewable energy, photovoltaic power generation has become a vital component of the power grid due to its cleanliness and flexibility. However, the volatility, intermittent nature, and distributed nature of photovoltaic access pose significant challenges to the planning and operation of traditional power grids. For example, when photovoltaic output is significantly affected by weather, grid node voltages frequently fluctuate, especially during periods of low load and high photovoltaic output, which can easily lead to voltage over-limit issues. Concentrated photovoltaic access areas can trigger reverse power flow, leading to line overloads or insufficient equipment capacity. Furthermore, the control characteristics of photovoltaic inverters do not match the inertia of the grid, potentially causing small-interference or transient instability in fault scenarios.

[0003] Traditional grid planning methods generally use static power flow analysis and lack refined modeling of dynamic processes. They have the following shortcomings: they rely solely on steady-state models and do not consider the coupling relationship between photovoltaic dynamic characteristics (such as inverter control response) and grid dynamic parameters (such as inertia and damping). In addition, the photovoltaic access scenario settings are simple and do not cover complex operating conditions such as capacity gradient changes and distributed and centralized hybrid access. There is a lack of real-time response prediction for transient faults such as short circuits and line tripping, resulting in large deviations between stability assessment results and actual operation. Summary of the Invention

[0004] In response to the problems mentioned in the prior art, the present invention proposes an evaluation method and related devices for distributed photovoltaic access to distribution networks, which can integrate multi-dimensional data, dynamically simulate photovoltaic access scenarios and accurately evaluate stability. By integrating multi-dimensional data such as geographic information, line parameters, substation capacity and transformer ratio, a steady-state and dynamically coupled power grid model is constructed, which solves the defect that the traditional single model cannot characterize the coupling relationship between the dynamic characteristics of photovoltaics and the inertia of the power grid.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for evaluating distributed photovoltaic access to a power distribution network, comprising the following steps: Obtain characteristic data of the target power grid; Constructing a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through the topological relationship between nodes and branches; Set up a PV access scenario and perform power flow calculations based on the grid steady-state model in this scenario. Obtain power flow calculation results for the grid. Use these results to identify voltage-limited areas and line overload risk points. Analyze PV access scenarios based on the grid dynamic model according to the voltage-limit-exceeding areas and line overload risk points of the grid, and evaluate the grid stability margin.

[0006] As a further improvement of the present invention, the characteristic data includes geographic information, line parameters, substation capacity and transformer ratio data of the target power grid.

[0007] As a further improvement of the present invention, a grid steady-state model and a grid dynamic model are established based on power system analysis software, and the power system analysis software is PSS / E or DIgSILENT.

[0008] As a further improvement of the present invention, the photovoltaic access scenario includes a gradient change of photovoltaic installed capacity and an adjustment of the access location, wherein the ratio of the gradient change of photovoltaic installed capacity ranges from 10% to 200% of the current regional load capacity; the access location adjustment includes distributed nodes and centralized busbars.

[0009] As a further improvement of the present invention, the inertia parameters of the grid and the dynamic characteristics of the controller of the grid dynamic model are used to simulate the frequency and voltage recovery process of the system after a fault, and dynamically adjust the active / reactive output of the photovoltaic inverter to maintain system stability.

[0010] As a further improvement of the present invention, the analysis of the photovoltaic access scenario includes small disturbance stability analysis and transient stability analysis.

[0011] As a further improvement of the present invention, the transient stability analysis includes recording transient fluctuation curves of grid frequency and voltage when simulating a short-circuit fault in a grid dynamic model, and determining whether the system is unstable based on a preset threshold value; When a line trip fault occurs, the power flow transfer path and cascading failure risk are predicted through the grid dynamic model, and a corresponding photovoltaic capacity adjustment plan is generated.

[0012] An evaluation system for distributed photovoltaic access to a distribution network, comprising: An acquisition module, used to acquire characteristic data of a target power grid; A construction module is used to construct a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through the topological relationship between nodes and branches; The calculation module is used to set up a photovoltaic access scenario, perform power flow calculations in the photovoltaic access scenario based on the grid steady-state model, obtain the power flow calculation results of the grid, and identify voltage-limited areas and line overload risk points of the grid based on the power flow calculation results; The evaluation module is used to analyze photovoltaic access scenarios based on the grid's voltage-limiting areas and line overload risk points based on the grid's dynamic model, and evaluate the grid's stability margin.

[0013] An evaluation device for distributed photovoltaic access to a power distribution network comprises a processor and a memory, wherein the processor implements the above-mentioned evaluation method for distributed photovoltaic access to a power distribution network when executing a computer program stored in the memory.

[0014] A computer-readable storage medium is used to store a computer program, wherein when the computer program is executed by a processor, it implements the above-mentioned evaluation method for distributed photovoltaic access to a power distribution network.

[0015] Compared with the prior art, the present invention has achieved the following technical effects: The present invention integrates multi-dimensional data such as geographic information, line parameters, substation capacity and transformer ratio to construct a steady-state and dynamically coupled power grid model, which solves the defect that the traditional single model cannot characterize the coupling relationship between photovoltaic dynamic characteristics and grid inertia. The steady-state power grid model accurately maps the power grid topology based on the node admittance matrix to ensure the accuracy of power flow calculation. The dynamic power grid model introduces photovoltaic inverter control logic, generator inertia constant and protection device action characteristics, which can simulate the dynamic recovery process of frequency and voltage after a fault.

[0016] The present invention comprehensively covers risks such as voltage over-limit, line overload, small disturbance instability and transient instability by combining the photovoltaic access scenarios it sets with various types of stability analysis tools. Based on the results of power flow calculations, it can identify voltage over-limit nodes and line overload hotspots, assess voltage and line risks, and accurately understand the safety margin of the system under different operating conditions, providing a basis for formulating effective risk management strategies. It quantifies system stability through small disturbance stability and transient stability, and quantitatively assesses the stability of the system, thereby achieving accurate quantification of the stability margin.

[0017] The present invention can predict the real-time response of the power grid and generate targeted optimization solutions. By adjusting the active / reactive output of photovoltaic inverters or configuring SVG devices, the frequency recovery time under transient faults can be reduced. At the same time, when simulating line tripping, the power grid dynamic model can predict the power flow transfer path to avoid cascading overload problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the evaluation method for distributed photovoltaic access to a power distribution network according to the present invention; Figure 2 Schematic diagram of the evaluation system for distributed photovoltaic access to the power distribution network of the present invention; Figure 3 The figure is a structural diagram of a computer device according to the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0020] like Figure 1 As shown, the present invention proposes an evaluation method for distributed photovoltaic access to a distribution network, comprising the following steps: Obtain characteristic data of the target power grid; Constructing a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through a topological relationship between nodes and branches; Set up a PV access scenario and perform power flow calculations based on the grid steady-state model in this scenario. Obtain power flow calculation results for the grid. Use these results to identify voltage-limited areas and line overload risk points. Analyze PV access scenarios based on the grid dynamic model according to the voltage-limit-exceeding areas and line overload risk points of the grid, and evaluate the grid stability margin.

[0021] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments: Step 1: Feature data collection and preprocessing. Feature data includes geographic information of the target power grid, line parameters, substation capacity and transformer ratio data.

[0022] The target grid's geographic information is obtained through a geographic information system (GIS) platform, including the target grid area's geographic coordinates, line alignment, substation locations, and elevation data. For example, a regional grid covers approximately 500 square kilometers and includes 15 substations, 120 nodes, and 85 transmission lines, all of which require their longitude and latitude coordinates to be annotated.

[0023] Line parameters include resistance (R), reactance (X), and capacitance (C) obtained from line design drawings or on-site measurements. For older lines, the aging factor (e.g., a 5% increase in resistance) must be considered, and parameter accuracy must be verified using frequency domain reflectometry (FDR).

[0024] Transformer parameters include the rated capacity (e.g., 500 MVA), the ratio (e.g., 220 / 110 kV), and the short-circuit impedance (e.g., 12%). For multi-winding transformers, the connection method of each winding must be separately indicated (e.g., YNd11).

[0025] Substation capacity is the statistical data of the main transformer capacity (such as 2×300 MVA), bus voltage level (such as 220kV, 110 kV) and load distribution of each substation.

[0026] Step 2: Construct a grid steady-state model and a grid dynamic model. Use PSS / E software to build a grid steady-state model. The specific process is as follows: Import the preprocessed electrical parameters into PSS / E and divide the nodes according to voltage levels (e.g., 220 kV nodes are marked as "BUS2201" and 110 kV nodes are marked as "BUS1101").

[0027] Set the base voltage value (e.g. 230 kV) and system frequency (50 Hz), and define the initial distribution of load power (e.g. the load at a node is 50 MW + j20 Mvar).

[0028] In PSS / E, create a Branch object and enter the resistance, reactance, capacitance, and length (e.g., 100 km). Create a Transformer object and set the ratio (e.g., 220 / 110 kV), rated capacity, and short-circuit impedance. For transformers with YNd11 connection, additionally specify the neutral grounding method.

[0029] Perform an initial power flow calculation to check whether the node voltages are within a reasonable range (0.95 to 1.05 pu). If a node voltage is abnormal (for example, 0.85 pu), investigate data input errors or topology connectivity issues.

[0030] Compare the measured data with the model output to check whether the model accuracy meets the requirements.

[0031] To build a dynamic grid model in DIgSILENT PowerFactory, follow these steps: Set the inertia constant (H=5 s) and damping factor (D=2%). For PV inverters: Select the "Dynamic Voltage Control" mode, configure the active / reactive power controller parameters, and define the overcurrent protection action time and reclosing logic.

[0032] Using DIgSILENT's "Compound Model" feature, we linked the steady-state model with the dynamic model, ensuring that both shared node and branch parameters. We verified the dynamic response of the coupled model by simulating a sudden drop in PV output (from 100% to 50%) and observing whether the frequency fluctuations were within ±0.5 Hz.

[0033] Step 3: PV access scenario settings Set the PV penetration rate gradient to 10%, 50%, 100%, 150%, and 200% of the regional load capacity. For example, if the regional load is 200 MW, the PV capacity is 20 MW, 100 MW, 200 MW, 300 MW, and 400 MW, respectively. Distribute PV capacity to the end nodes of the distribution network to simulate rooftop PV scenarios. Connect a large PV power station to a high-voltage bus (e.g., 220 kV) to simulate a centralized power generation scenario.

[0034] Based on the grid topology, key nodes are selected for access testing to evaluate their impact on voltage support.

[0035] The Newton-Raphson iteration method is used to solve the nonlinear power flow equation, and the output results include node voltage amplitude, phase angle, line active / reactive power and loss.

[0036] The voltage safety threshold is set to ±10% (0.9-1.1 pu). If the voltage at a node reaches 0.87 pu, it is marked as exceeding the limit and requires adjusting the PV output or installing a voltage regulator.

[0037] Calculate the load factor based on the line's thermal stability limit. If it exceeds 90%, it is considered overloaded. Redistribute PV output or activate a backup line.

[0038] Step 4: Based on the grid dynamic model, perform small-disturbance stability analysis and transient stability analysis on the PV access scenario according to the grid voltage over-limit areas and line overload risk points. Evaluate the grid's dynamic response and stability margin under short-circuit or line tripping faults.

[0039] Small-disturbance stability analysis involves performing a modal analysis in DIgSILENT to extract the eigenvalues of the system state matrix. If the real part of the eigenvalue, σ, is greater than 0, the system is at risk of oscillation instability and requires adjustment of the PV controller parameters to suppress oscillation.

[0040] Calculate the damping ratio and determine whether it is a weak damping mode or a strong damping mode based on the damping ratio. If it is a weak damping mode, it is necessary to add a reactive compensation device to improve the damping.

[0041] Transient stability analysis involves setting a three-phase short-circuit fault at a key node (such as a 220 kV bus) with a duration of 0.1 seconds. Grid frequency, voltage, and generator power angle curves are collected during the fault period. For example, a fault may cause the frequency to drop to 49.3 Hz and the voltage to 0.6 pu. However, the dynamic reactive power support provided by the PV inverter allows the frequency to recover to 49.8 Hz within 0.5 seconds.

[0042] Simulates a line tripping due to overload, triggering power flow transfer to adjacent lines. If the load rate of an adjacent line exceeds 100%, the risk of its tripping is further simulated and an early warning is generated.

[0043] Dynamically adjust the active / reactive output of the PV inverter during transient conditions. Improve fault ride-through capability by installing dynamic reactive power compensation devices or energy storage systems.

[0044] The following embodiments are specific applications.

[0045] A coastal power grid consists of 80 nodes, 60 lines, a peak load of 500 MW, and an existing PV capacity of 100 MW. A steady-state model was established in PSS / E, and a dynamic model was expanded in DIgSILENT to include five PV inverters and three synchronous generators.

[0046] When the PV capacity increased to 200 MW, the power flow calculation showed that the voltage at three nodes exceeded the limit (0.88 pu) and two lines were overloaded (load factor 92%).

[0047] Transient analysis shows that the frequency drops to as low as 49.0 Hz during a short-circuit fault. By configuring a 15 MVar SVG and optimizing inverter control, the time required for the frequency to recover to 49.5 Hz is reduced from 2.5 seconds to 1.2 seconds.

[0048] Improved voltage stability: The number of out-of-limit nodes was reduced by 75%, and the average voltage deviation was reduced from 8% to 2%.

[0049] Optimized line utilization: The number of overloaded lines was reduced by 60%, and transmission efficiency was improved by 12%.

[0050] Enhanced fault recovery capability: The risk of transient instability is reduced by 50%, and the maximum PV penetration rate that the system can withstand is increased from 150% to 250%.

[0051] This method has wide applicability in power system planning and renewable energy grid integration, and is particularly suitable for diverse scenarios such as grids with a high proportion of renewable energy, microgrids and islanded operation, and urban distribution network upgrades. By predicting the real-time response of the grid and generating targeted optimization plans, it can reduce frequency recovery time under transient faults by adjusting the active / reactive output of photovoltaic inverters or configuring SVG devices. When simulating line tripping, the dynamic model can predict the flow transfer path to avoid cascading overload problems.

[0052] Based on the same inventive concept, an embodiment of the present invention also provides an evaluation system for distributed photovoltaic access to a distribution network. Since the principle of solving the problem by the evaluation system for distributed photovoltaic access to a distribution network is similar to the aforementioned evaluation method for distributed photovoltaic access to a distribution network, the implementation of the evaluation system for distributed photovoltaic access to a distribution network can refer to the implementation of the evaluation method for distributed photovoltaic access to a distribution network, and the repeated parts will not be repeated.

[0053] In specific implementation, the evaluation system for distributed photovoltaic access to a distribution network provided by the embodiment of the present invention specifically includes: An acquisition module, used to acquire characteristic data of a target power grid; A construction module is used to construct a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through the topological relationship between nodes and branches; The calculation module is used to set up a photovoltaic access scenario, perform power flow calculations in the photovoltaic access scenario based on the grid steady-state model, obtain the power flow calculation results of the grid, and identify voltage-limited areas and line overload risk points of the grid based on the power flow calculation results; The evaluation module is used to analyze photovoltaic access scenarios based on the grid's voltage-limiting areas and line overload risk points based on the grid's dynamic model, and evaluate the grid's stability margin.

[0054] Accordingly, an embodiment of the present invention further provides an evaluation device for distributed photovoltaic access to a distribution network, comprising a processor and a memory, wherein the processor implements an evaluation method for distributed photovoltaic access to a distribution network as provided in an embodiment of the present invention when executing a computer program stored in the memory.

[0055] For more specific details about the above method, please refer to the corresponding contents disclosed in the aforementioned embodiments, which will not be described again here.

[0056] Accordingly, an embodiment of the present invention further provides a computer-readable storage medium for storing a computer program, wherein when the computer program is executed by a processor, the evaluation method for accessing a distributed photovoltaic power distribution network as provided in an embodiment of the present invention is implemented.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. References to the same or similar portions of the various embodiments will be sufficient. The systems, devices, and storage media disclosed in the embodiments are described briefly because they correspond to the methods disclosed in the embodiments. For relevant details, refer to the method descriptions.

[0058] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0059] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0060] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0061] The above is a detailed introduction to the evaluation method, system, device and storage medium for distributed photovoltaic access to the distribution network provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for evaluating distributed photovoltaic access to a distribution network, characterized in that: The following steps are involved: Obtain characteristic data of the target power grid; Constructing a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through a topological relationship between nodes and branches; Set up a PV access scenario and perform power flow calculations based on the grid steady-state model in this scenario. Obtain power flow calculation results for the grid. Use these results to identify voltage-limited areas and line overload risk points. Analyze PV access scenarios based on the grid dynamic model according to the voltage-limit-exceeding areas and line overload risk points of the grid, and evaluate grid stability.

2. The evaluation method for distributed photovoltaic access to a distribution network according to claim 1, characterized in that: The characteristic data includes geographic information, line parameters, substation capacity and transformer ratio data of the target power grid.

3. The evaluation method for distributed photovoltaic access to a distribution network according to claim 1, characterized in that: A grid steady-state model and a grid dynamic model are established according to power system analysis software, wherein the power system analysis software is PSS / E or DIgSILENT.

4. The evaluation method for distributed photovoltaic access to a distribution network according to claim 1, characterized in that: PV access scenarios include PV installed capacity gradient changes and access location adjustments, where the proportion of PV installed capacity gradient changes ranges from 10% to 200% of the current regional load capacity; Access location adjustment includes distributed nodes and centralized busbars.

5. The evaluation method for distributed photovoltaic access to a distribution network according to claim 1, characterized in that: The inertia parameters of the grid and the dynamic characteristics of the controller in the grid dynamic model are used to simulate the frequency and voltage recovery process of the system after a fault, and dynamically adjust the active / reactive output of the photovoltaic inverter to maintain system stability.

6. The evaluation method for distributed photovoltaic access to a distribution network according to claim 1, characterized in that: The analysis of photovoltaic access scenarios includes small disturbance stability analysis and transient stability analysis.

7. The method for evaluating distributed photovoltaic access to a distribution network according to claim 6, characterized in that: The transient stability analysis includes recording transient fluctuation curves of grid frequency and voltage when simulating a short-circuit fault in a grid dynamic model, and determining whether the system is unstable based on a preset threshold value; When a line trip fault occurs, the power flow transfer path and cascading failure risk are predicted through the grid dynamic model, and a corresponding photovoltaic capacity adjustment plan is generated.

8. An evaluation system for distributed photovoltaic access to a distribution network, characterized in that: include: An acquisition module, used to acquire characteristic data of a target power grid; A construction module is used to construct a grid steady-state model and a grid dynamic model based on the characteristic data, wherein the grid steady-state model and the grid dynamic model are coupled through the topological relationship between nodes and branches; The calculation module is used to set up a photovoltaic access scenario, perform power flow calculations in the photovoltaic access scenario based on the grid steady-state model, obtain the power flow calculation results of the grid, and identify voltage-limited areas and line overload risk points of the grid based on the power flow calculation results; The evaluation module is used to analyze photovoltaic access scenarios based on the grid's voltage-limiting areas and line overload risk points based on the grid's dynamic model, and evaluate the grid's stability margin.

9. An evaluation device for distributed photovoltaic access to a distribution network, characterized in that: The method comprises a processor and a memory, wherein when the processor executes the computer program stored in the memory, the method for evaluating the access of distributed photovoltaic power generation to a power distribution network as claimed in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that Used to store a computer program, wherein when the computer program is executed by a processor, the evaluation method for accessing a distributed photovoltaic power distribution network according to any one of claims 1 to 7 is implemented.

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