Method and device for evaluating broadband oscillation of distribution network rich in distributed power supply

Abstract

The present application relates to the technical field of power distribution, in particular to a kind of distributed power supply rich distribution network broadband oscillation evaluation method and device.Method includes: obtaining the basic parameters of distribution network, topological layering is carried out according to voltage level, and output layering node correlation matrix;Based on layering node correlation matrix, the equivalent norton model of point of common coupling is constructed;For each frequency band: based on the initial stability margin of distribution network under the frequency band of point of common coupling equivalent admittance and upper grid Thevenin impedance is calculated;Based on source load coupling strength, the initial stability margin is corrected to obtain the final stability margin;Based on the final stability margin, the oscillation risk level of the frequency band is determined, when the oscillation risk level is greater than the preset safety level, the distribution network is analyzed by tracing source;For each operating condition of distribution network, the determination process of oscillation risk level is repeated to determine the safe operation boundary of distribution network.The present application can accurately evaluate the oscillation risk of distribution network and trace source adjustment.

Description

Technical Field

[0001] This invention relates to the field of power supply and distribution technology, and in particular to a method and apparatus for evaluating broadband oscillations in distributed power source-rich distribution networks. Background Technology

[0002] Against the backdrop of the accelerated construction of new power systems, large-scale distributed power sources have become highly concentrated on the distribution network side. Currently, photovoltaic, wind power, and energy storage inverter units are widely connected in 10kV / 380V distribution areas, and the installed capacity and penetration rate of new energy sources continue to rise. Distributed generation is showing a large-scale development trend characterized by "numerous points, wide coverage, and dispersion." However, this high proportion and multi-type distributed power source grid connection has also profoundly changed the operating environment of the distribution network—the system exhibits five typical characteristics: coexistence of multiple types of heterogeneous equipment, extremely dispersed geographical distribution, complex radial multi-level collection structure, strong spatiotemporal fluctuations on both the source and load sides, and multi-link coupling oscillations of the "source-grid-load" system. Among these, the 2~1000Hz full-band broadband oscillation problem caused by multi-link interaction is the most prominent. Its wide frequency band and complex propagation path have seriously threatened the stable operation of the distribution network and have become one of the core challenges facing the safety control of the current new distribution system.

[0003] Currently, most existing methods for assessing broadband oscillations in distribution networks remain at the level of rough risk level judgment. They cannot achieve quantitative assessment by frequency band, nor can they effectively account for the impact of dynamic coupling between the source and load on oscillation characteristics. The accuracy of the assessment results is low, and the source of the oscillation cannot be quickly located after an accident. This has led to accidents such as batch inverter disconnection from the grid, false tripping of line protection, and continuous voltage oscillation in distribution areas in many places.

[0004] Therefore, there is an urgent need for a method and device for evaluating broadband oscillations in distributed power generation-rich distribution networks to solve the above problems. Summary of the Invention

[0005] This invention provides a method and apparatus for assessing broadband oscillations in a distributed power source-enriched distribution network, which can accurately assess the risk level of the distribution network and accurately trace its source.

[0006] In a first aspect, embodiments of the present invention provide a method for evaluating broadband oscillations in a distributed power generation-rich distribution network, comprising: S1. Obtain the basic parameters of the distribution network, and perform topological layering of the distribution network according to voltage level, and output the layered node association matrix; S2, based on the hierarchical node association matrix, the distributed power sources and loads in the distribution network are respectively constructed as port Norton models with controlled current sources, and the lines are constructed as π-type equivalent models. Through admittance merging, branch equivalent transformation and intermediate node elimination, the equivalent Norton model of the distribution network common connection point is obtained. S3, divide the frequency oscillation range of the power distribution network into multiple frequency bands, and perform the following for each frequency band: Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the initial stability margin of the distribution network in this frequency band is calculated; the stability margin includes phase margin and magnitude margin. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. S4. For each operating condition of the distribution network, repeat the process of determining the oscillation risk level in step S3 to determine the safe operating boundary of the distribution network based on the critical operating conditions that meet the preset safety level.

[0007] Secondly, embodiments of the present invention also provide a broadband oscillation assessment device for distributed power source enrichment distribution networks, comprising: The acquisition unit is used to acquire the basic parameters of the distribution network, perform topological layering of the distribution network according to voltage level, and output the layered node association matrix; The construction unit is used to construct the distributed power sources and loads in the distribution network as port Norton models with controlled current sources and the lines as π-type equivalent models based on the hierarchical node association matrix. The equivalent Norton model of the distribution network common connection point is obtained by admittance merging, branch equivalent transformation and intermediate node elimination. The evaluation unit is used to divide the frequency oscillation range of the distribution network into multiple frequency bands, and for each frequency band, performs the following: Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the initial stability margin of the distribution network in this frequency band is calculated; the stability margin includes phase margin and magnitude margin. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. The boundary determination unit is used to repeatedly execute the oscillation risk level determination process in the evaluation unit for each operating condition of the distribution network, so as to determine the safe operating boundary of the distribution network based on the critical operating condition that meets the preset safety level.

[0008] Thirdly, embodiments of the present invention also provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the method described in any embodiment of this specification.

[0009] Fourthly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the methods described in any embodiment of this specification.

[0010] Fifthly, embodiments of the present invention also provide a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described above.

[0011] This invention provides a method and apparatus for evaluating broadband oscillations in a distributed power source-enriched distribution network. First, by constructing distributed power sources and loads in the distribution network as port Norton models with controlled current sources, and constructing lines as π-type equivalent models, and through admittance merging, branch equivalent transformation, and intermediate node elimination, hierarchical Norton aggregation modeling can be simplified, avoiding complex full-order modeling, and reducing the original thousand-order full-node model to a PCC single-node equivalent model. Thus, only frequency-domain sweep data from the device ports is needed as the main input to the equivalent Norton model, without requiring internal control codes or complete state-space models from different manufacturers. This allows for reflecting the impact of multi-level radiating topology on source-network interaction while reducing the model order. Second, frequency-band evaluation can improve the accuracy of the evaluation results. Furthermore, by combining the stability margins of multiple frequency bands with source-load coupling correction, and further using the evaluation results for solving the safe operating boundary under multiple operating conditions and joint tracing of the participation factor-impedance contribution, an analytical link can be formed that interconnects pre-emptive boundary determination, operational risk warning, and post-fault location. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the structure of a distributed power source-enriched distribution network broadband oscillation evaluation method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of voltage phase angle fluctuation curves of multiple nodes in a power distribution network when the source adjustment is not performed using the method of this application, according to an embodiment of the present invention. Figure 3This is an embodiment of the present invention that uses the method of this application to... Figure 2 A schematic diagram of voltage phase angle fluctuation curves at multiple nodes after source tracing adjustments; Figure 4 This is a comparative schematic diagram showing the operation boundary determined by the method of the present invention and other existing methods, according to an embodiment of the present invention. Figure 5 This is a hardware architecture diagram of an electronic device provided in an embodiment of the present invention; Figure 6 This is a structural diagram of a distributed power source enrichment distribution network broadband oscillation evaluation device provided in an embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] Please refer to Figure 1 This invention provides a method for evaluating broadband oscillations in distributed generation-rich distribution networks, the method comprising: Step S1: Obtain the basic parameters of the distribution network, and perform topological layering of the distribution network according to voltage level, and output the layered node association matrix; Step S2: Based on the hierarchical node association matrix, the distributed power sources and loads in the distribution network are respectively constructed as port Norton models with controlled current sources, and the lines are constructed as π-type equivalent models. Through admittance merging, branch equivalent transformation and intermediate node elimination, the equivalent Norton model of the distribution network common connection point is obtained. Step S3: Divide the frequency oscillation range of the distribution network into multiple frequency bands, and perform the following for each frequency band: Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the initial stability margin of the distribution network in this frequency band is calculated; the stability margin includes phase margin and magnitude margin. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. Step S4: For each operating condition of the distribution network, repeat the process of determining the oscillation risk level in step S3 to determine the safe operating boundary of the distribution network based on the critical operating conditions that meet the preset safety level.

[0016] In this embodiment, firstly, by constructing distributed power sources and loads in the distribution network as port Norton models with controlled current sources and constructing lines as π-type equivalent models, and through admittance merging, branch equivalent transformation, and intermediate node elimination, hierarchical Norton aggregation modeling can be simplified, avoiding complex full-order modeling, and reducing the original thousand-order full-node model to a PCC single-node equivalent model. Thus, only frequency sweep data from the device ports is needed as the main input to the equivalent Norton model, without requiring internal control codes or complete state-space models from different manufacturers. This allows for the reduction of model order while reflecting the impact of multi-level radiating topology on source-network interaction. Secondly, frequency-band evaluation can improve the accuracy of the evaluation results. Furthermore, by combining the stability margins of multiple frequency bands with source-load coupling correction, and further using the evaluation results for multi-condition safe operation boundary solving and joint tracing of participation factor-impedance contribution, an analytical link can be formed that interconnects pre-emptive boundary determination, operational risk warning, and post-fault location.

[0017] The following description Figure 1 The execution method for each step is shown.

[0018] First, for step S1, the basic parameters of the distribution network are obtained, and the distribution network is topologically layered according to voltage level, and the layered node association matrix is ​​output.

[0019] In this step, the basic parameters of the distribution network include: distributed generation parameters, load parameters and load fluctuation characteristics, line parameters, transformer parameters, short-circuit impedance of the upstream grid, and voltage level parameters. Voltage levels include the low-voltage distribution area level, feeder level, and substation level. Distributed generation parameters include rated capacity, port frequency domain sweep data, and control parameters. Furthermore, 10kV feeders are preferred for the feeder level, and 35kV substations are preferred for the substation level. Therefore, low-voltage distribution area parameters mainly include the distribution area transformer; feeder level parameters mainly include the resistance, inductance, and capacitance to ground of 10kV branch cables; and 35kV substation level parameters mainly include the impedance of the 35kV substation transformer.

[0020] Regarding step S2, since the distributed rich-central low-voltage distribution network is a multi-level radial topology: 380V distribution area, 10kV feeder and 35kV collection station, and a single area can have hundreds to thousands of inverters, energy storage and distributed wind turbines, and the complete dq state matrix of each device contains dozens of variables. Therefore, if not simplified, the model order after the entire system is connected exceeds tens of thousands of orders, which has two fatal problems: (1) Huge amount of calculation: the amount of calculation for matrix inversion, eigenvalue decomposition and frequency domain scanning increases exponentially. A single broadband evaluation of a normal workstation takes several hours, which cannot meet the engineering requirements of online real-time early warning of dispatch and rapid verification of distributed power supply access. (2) Redundant information interferes with broadband analysis: secondary dynamics such as inverter inner loop limiting, slow reactive power regulation and ultra-low frequency control only affect low frequency fluctuations within 0.1Hz, and have no effect on broadband oscillations of 2~1000Hz. The complete model carries a large number of irrelevant variables, which will cause distortion of frequency domain curves and offset of resonance point calculation, which will reduce the accuracy of oscillation evaluation. Based on this, this step simplifies the distributed, centralized low-voltage distribution network, and the simplification process is as follows: Based on the hierarchical node association matrix, the distributed power sources and loads in the distribution network are constructed as port Norton models with controlled current sources, and the lines are constructed as π-type equivalent models. Through admittance merging, branch equivalent transformation, and intermediate node elimination, the equivalent Norton model of the distribution network's point of common connection is obtained. The equivalent Norton model is as follows: In the formula, for Equivalent admittance at the moment of common connection point; for Time of the first Equivalent admittance of a distributed power source For the number of distributed power sources, for Equivalent admittance of the current collector network at any time for Equivalent admittance at any given time.

[0021] This step abandons the complex full-order modeling approach, retaining only the core dynamic features related to broadband oscillations. A three-level hierarchical simplified aggregation framework is constructed, which can reduce the original thousand-order full-node model to an equivalent model of a common connection point (PCC single node). This eliminates the need to obtain internal device control code, balancing modeling efficiency and evaluation accuracy, and providing a reliable foundation for the quantitative evaluation of broadband oscillations. Based on this, combined with subsequent frequency-band evaluation algorithms, the stability margin calculation speed can be improved by 80–120 times, meeting the requirements for online real-time stability verification of scheduling, rapid evaluation of distributed power supply expansion, and real-time risk warning.

[0022] For step S3, the frequency oscillation range of the distribution network is 2~1000Hz, which can be divided into three frequency bands: 2~10Hz (low frequency), 10~100Hz (medium frequency), and 100~1000Hz (high frequency). The Nyquist curves for each frequency band are then plotted. For each frequency band, the following operations are performed: A1. Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid in the equivalent Norton model, calculate the initial stability margin of the distribution network in this frequency band; the stability margin includes phase margin and magnitude margin.

[0023] In this step, firstly, based on the rated voltage of the distribution network and the short-circuit capacity of the upstream grid, the Thevenin impedance of the upstream grid is calculated as follows: Then, based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the source-grid cross-impedance transfer matrix is ​​constructed as follows: In the formula, The Thevenin impedance of the upstream power grid, This is the rated voltage of the power distribution network. For the short-circuit capacity of the upstream power grid; This is the source-network cross impedance transfer matrix.

[0024] Based on the constructed source-network cross-impedance transfer matrix, the initial phase margin is calculated using the following formula: In the formula, This is the initial phase margin; Source-network cross impedance transfer matrix The angular frequency corresponding to an amplitude of 1, i.e., the amplitude crossover frequency; It is the imaginary unit.

[0025] Based on the constructed source-network cross-impedance transfer matrix, the initial gain margin is calculated using the following formula: In the formula, This is the initial gain margin; Source-network cross impedance transfer matrix The angular frequency corresponding to a phase of -180°, i.e., the phase crossover frequency; It is the imaginary unit.

[0026] In addition, this step can also be used to calculate the damping coefficient based on the following formula: In the formula, The damping coefficient is... Let be the real part of the eigenvalues ​​of the oscillation mode. ω is the oscillation angular frequency.

[0027] A2. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band.

[0028] In this step, the source-load coupling strength is first calculated based on the following formula: Then, based on the source-load coupling strength, the initial stability margin is corrected using the following formula: In the formula, for Source-load coupling strength at any given time; for Momentary load equivalent admittance; for Equivalent admittance at the moment of common connection point; and They are respectively Initial phase margin and initial gain margin at time t; and They are respectively The final phase margin and final magnitude margin at each time step.

[0029] It should be noted that the source-load coupling strength The larger the value, the more stable the power distribution network.

[0030] A3. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined. The specific implementation process is as follows: A31, Set the initial phase warning threshold Initial phase high-risk threshold Amplitude warning threshold and high-risk threshold for amplitude Prioritize this area. , , , .

[0031] A32, determine whether the source-load coupling strength is greater than a preset coupling strength threshold. If not, then the initial phase warning threshold is used as the final phase warning threshold, and the initial phase high-risk threshold is used as the final phase high-risk threshold; if yes, then both the initial phase warning threshold and the initial phase high-risk threshold are increased by a preset angle. The final phase warning threshold and the final phase high-risk threshold are obtained.

[0032] For example, when At that time, take , ; when hour, , ; In the formula, The preset coupling strength threshold is preferably 0.8; Preferred angle , Final phase warning threshold, This is the final high-risk threshold for the phase.

[0033] It should be noted that users can determine the values ​​of the above parameters as needed, and this application is not limited to the above parameters.

[0034] A33. Based on the numerical relationship between the final phase margin, the final phase warning threshold, and the final phase high-risk threshold, the phase risk level of the distribution network is determined.

[0035] In this step, if Therefore, the phase risk level of the distribution network is determined to be Level 1, i.e., low oscillation risk, denoted as... ; like When this occurs, the phase risk level of the distribution network is determined to be Level II, i.e., early warning of oscillation risk, denoted as... ; like Therefore, the phase risk level of the distribution network is determined to be Level 3, i.e., high-risk oscillation risk, denoted as... .

[0036] A34. Based on the numerical relationship between the final amplitude margin, the amplitude warning threshold, and the amplitude high-risk threshold, the amplitude risk level of the distribution network is determined.

[0037] In this step, if Therefore, the amplitude risk level of the distribution network is determined to be Level 1, i.e., low oscillation risk, denoted as... ; like When this occurs, the amplitude risk level of the distribution network is determined to be Level II, i.e., early warning of oscillation risk, denoted as... ; like Therefore, the amplitude risk level of the distribution network is determined to be Level III, i.e., high-risk oscillation risk, denoted as... .

[0038] A35, the higher of the phase risk level and the amplitude risk level is taken as the oscillation risk level of the distribution network in this frequency band, that is: .

[0039] In the formula, The risk level is oscillation. Phase risk level, It is classified as amplitude risk level.

[0040] It should also be noted that after determining the oscillation risk level R, an oscillation amplitude correction factor can be introduced. The oscillation risk level R is revised, where, A is the actual oscillation amplitude. This is the rated voltage amplitude; when When this happens, the oscillation risk level R is raised by one level. By adjusting the risk level in conjunction with the actual operating status of the power grid, the accuracy of risk assessment can be further improved.

[0041] This step, by constructing a differentiated risk classification system and correcting the risk threshold based on source-load coupling characteristics, can accurately classify three levels of risk: low risk, early warning risk, and high-risk oscillation. It ensures that the risk assessment error of the oscillation across the entire frequency band from 2 to 1000 Hz is ≤5%, accurately identifies the differences in oscillation risk across different frequency bands, and solves the problems of low assessment accuracy and ambiguous risk judgment in existing technologies. The assessment results are more in line with the actual operating conditions of the distribution network, providing guidance for the operation of the distribution network.

[0042] A4. When the oscillation risk level is greater than the preset safety level, a source analysis of the distribution network is performed. The specific process is as follows: Calculate the participation factor for each node in the hierarchical node association matrix, and designate nodes with participation factors greater than a set threshold as core nodes. The participation factor calculation process is as follows: In the formula, For the first The participation factor of each node , The first The and the first The right eigenvector of each node. , The first The and the first The left feature vector of each node, This represents the total number of nodes. If... If so, the node is determined to be a core node, and a threshold is set. 0.6 is preferred.

[0043] Calculate the total impedance of all devices at all core nodes, denoted as . .

[0044] For each device in the distribution network, its contribution is calculated based on the participation factor of its corresponding node, port impedance, and total impedance, as follows: In the formula, For the first The contribution of each device; For the first The participation factor of each device corresponding to a node. For the first Port impedance of each device. This represents the total impedance of all devices at all core nodes.

[0045] The device that contributes the most to the overall oscillation is designated as the core oscillation device. Increase the inverter damping coefficient of the core oscillation device to ensure that the adjusted damping coefficient meets the low-risk requirements of wideband oscillation. For example, increase the inverter damping coefficient of the core oscillation device. Increase it by 0.1, so that the corrected damping coefficient is denoted as... Of course, increasing it by 0.1 is only one preferred method, and it is not the only option here. It should be noted that the preset safety level is Level 1 risk, i.e., low oscillation risk.

[0046] This step, through the aforementioned tracing method, can locate core nodes, equipment, and coupling links within 5 minutes, with a tracing accuracy rate of no less than 95%. At the same time, it generates targeted rectification suggestions, filling the gaps in existing technologies that cannot trace sources, significantly shortening the time for handling oscillation faults, and reducing the economic losses caused by line tripping and unit disconnection from the grid.

[0047] For step S4, determining the safe operation boundary of the distribution network includes: The range of distributed power penetration (e.g., 0~80%), the range of load fluctuation (e.g., ±30%), and the range of source-load coupling strength (e.g., 0.3~0.8) are discretized into multiple combined operating conditions; Determine the oscillation risk level of each operating condition combination in each frequency band; Search for critical combination working conditions that meet the preset safety level in at least one working condition dimension; the preset safety level is low risk level. The maximum allowable installed capacity of distributed power sources, the allowable load fluctuation range, the minimum energy storage capacity, and the allowable source-load coupling strength range are determined based on the critical combination operating conditions.

[0048] For example, when the distributed generation penetration rate is between 0-60%, the load fluctuation range is ±25%, and the source-load coupling strength range is 0.5-0.8, the distribution network can be guaranteed to always be at a low-risk level. Therefore, the safe operation boundary of the distribution network is: power generation penetration rate not exceeding 60%, load fluctuation range not exceeding 25%, and source-load coupling strength range not less than 0.5. Then, based on these boundaries, the maximum allowable installed capacity of distributed generation and the minimum configuration capacity of energy storage are determined.

[0049] This step, by solving the oscillation operation boundary under multiple operating conditions, can clarify the operating constraints of the distribution network, transforming the wideband oscillation control of the distribution network from post-fault review to proactive defense, thereby improving the stability of the distribution network's oscillation operation.

[0050] To demonstrate the effectiveness of the evaluation in this application, the inventors verified the operating curves of different nodes in a power distribution network, such as... Figure 2 and Figure 3 As shown. From Figure 2 It can be seen that when the method of this application is not used for source tracing and adjustment, the voltage phase angle of each node fluctuates significantly at certain frequencies. However, after using the method of this application for source tracing and adjusting the damping coefficient, the voltage phase angle fluctuation can be significantly reduced, ensuring the stable operation of the distribution network. Figure 4 As shown, the stability boundaries determined using the method of this application and other existing methods (different Lyapunov methods and equal-area methods) are illustrated. The horizontal axis represents the system power angle at the moment of fault clearing under broadband oscillation conditions, and the vertical axis represents the corresponding angular velocity deviation. In the figure, the physical simulation stability boundary (red solid line) represents the true stability domain boundary, serving as a benchmark for evaluating the accuracy of various analytical methods. The internal region enclosed by the closed curve represents the transient stability region determined by the corresponding method. If the system state point during broadband oscillation falls within this region, the system is considered transiently stable; otherwise, synchronous instability occurs. The results in the figure show that the traditional Lyapunov method provides the smallest stability domain range, exhibiting significant conservatism. While it avoids misjudging instability conditions as stable, it significantly underestimates the actual transient stability capability of the system. The improved Lyapunov method expands the stability domain estimation range, but still deviates significantly from the true boundary. The improved equal-area method further improves the estimation accuracy, bringing the stability domain outline closer to the true boundary, achieving a certain trade-off between conservatism and estimation accuracy. The stable region area obtained by the equal area method (purple) with neglect of damping is the largest, but some boundaries extend outward beyond the real stable region. This is a non-conservative estimate and there is a risk of misjudging the actual unstable condition as stable, which poses a safety hazard in engineering applications.

[0051] Compared to the methods mentioned above, the stability domain profile of this patented analysis method is closest to the real stability boundary obtained from physical simulation. It avoids the overly conservative approach of traditional methods that compress the available stability margin of the system, and it also avoids the risk of misjudgment caused by boundary expansion due to neglecting damping schemes. It can not only support the determination of steady-state operating boundaries, but also significantly improve the estimation accuracy of transient stability attraction domain while ensuring the safety of engineering judgment, thus achieving the optimal balance between conservatism and estimation accuracy.

[0052] like Figure 5 , Figure 6 As shown, this embodiment of the invention provides a broadband oscillation assessment device for distributed power source-enriched distribution networks. The device embodiment can be implemented through software, hardware, or a combination of both. From a hardware perspective, as... Figure 5 The diagram shown is a hardware architecture diagram of an electronic device used in a distributed power source enrichment distribution network broadband oscillation assessment device according to an embodiment of the present invention. (Except for...) Figure 5 In addition to the processor, memory, network interface, and non-volatile memory shown, the electronic device in the embodiment may also include other hardware, such as a forwarding chip responsible for processing packets. Taking software implementation as an example, such as... Figure 6 As shown, a device in a logical sense is formed by the CPU of the electronic device in which it is located reading the corresponding computer program from the non-volatile memory into the memory for execution.

[0053] This embodiment provides a broadband oscillation assessment device for distributed power source-enriched distribution networks, comprising: The acquisition unit 600 is used to acquire the basic parameters of the distribution network, perform topological layering of the distribution network according to voltage level, and output the layered node association matrix. The construction unit 602 is used to construct the distributed power sources and loads in the distribution network as port Norton models with controlled current sources and the lines as π-type equivalent models based on the hierarchical node association matrix. The equivalent Norton model of the distribution network common connection point is obtained by admittance merging, branch equivalent transformation and intermediate node elimination. Evaluation unit 604 is used to divide the frequency oscillation range of the distribution network into multiple frequency bands, and for each frequency band, perform the following: Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the initial stability margin of the distribution network in this frequency band is calculated; the stability margin includes phase margin and magnitude margin. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. The boundary determination unit 606 is used to repeatedly execute the oscillation risk level determination process in the evaluation unit for each operating condition of the distribution network, so as to determine the safe operating boundary of the distribution network based on the critical operating condition that meets the preset safety level.

[0054] In some implementations, the basic parameters of the distribution network include: distributed generation parameters, load parameters and load fluctuation characteristics, line parameters, transformer parameters, short-circuit impedance of the upstream grid, and voltage level parameters; the voltage level includes the low-voltage substation level, the feeder level, and the collection station level.

[0055] In some implementations, the equivalent Norton model is: In the formula, for Equivalent admittance at the moment of common connection point; for Time of the first Equivalent admittance of a distributed power source For the number of distributed power sources, for Equivalent admittance of the current collector network at any time for Equivalent admittance at any given time.

[0056] In some implementations, the source-load coupling strength is determined based on the following formula: Based on the source-load coupling strength, the initial stability margin is corrected using the following formula: In the formula, for Source-load coupling strength at any given time; for Momentary load equivalent admittance; for Equivalent admittance at the moment of common connection point; and They are respectively Initial phase margin and initial gain margin at time t; and They are respectively The final phase margin and final magnitude margin at each time step.

[0057] In some implementations, determining the oscillation risk level of the frequency band based on the final stability margin and the source-load coupling strength includes: Set differentiated risk thresholds, including initial phase warning threshold, initial phase high-risk threshold, amplitude warning threshold, and amplitude high-risk threshold; Determine whether the source-load coupling strength is greater than a preset coupling strength threshold. If not, use the initial phase warning threshold as the final phase warning threshold and the initial phase high-risk threshold as the final phase high-risk threshold. If yes, increase both the initial phase warning threshold and the initial phase high-risk threshold by a preset angle to obtain the final phase warning threshold and the final phase high-risk threshold. Based on the numerical relationship between the final phase margin and the final phase warning threshold and the final phase high-risk threshold, determine the phase risk level of the distribution network. The amplitude risk level of the distribution network is determined based on the numerical relationship between the final amplitude margin, the amplitude warning threshold, and the amplitude high-risk threshold. The higher of the phase risk level and the amplitude risk level is taken as the oscillation risk level of the distribution network in this frequency band.

[0058] In some implementations, when the oscillation risk level is greater than the preset safety level, the distribution network is analyzed for its source in the following way: Calculate the participation factor of each node in the hierarchical node association matrix, and designate nodes with participation factors greater than a set threshold as core nodes; Calculate the total impedance of all devices at all core nodes; For each device in the power distribution network, the device contribution is calculated based on the participation factor of its corresponding node, port impedance, and the total impedance. The device that contributes the most to the overall oscillation is designated as the core oscillation device. Increase the inverter damping coefficient of the core oscillation device to ensure that the adjusted damping coefficient meets the low-risk requirements of wideband oscillation.

[0059] In some implementations, determining the safe operating boundary of the distribution network includes: The range of variation in distributed power penetration, load fluctuation, and source-load coupling strength is discretized into multiple combined operating conditions. Determine the oscillation risk level of each operating condition combination in each frequency band; Search for critical combination working conditions that satisfy the preset safety level in at least one working condition dimension; The maximum allowable installed capacity of distributed power sources, the allowable load fluctuation range, the minimum energy storage capacity, and the allowable source-load coupling strength range are determined based on the critical combination operating conditions.

[0060] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on a broadband oscillation assessment device for a distributed power source-enriched distribution network. In other embodiments of the present invention, a broadband oscillation assessment device for a distributed power source-enriched distribution network may include more or fewer components than illustrated, or combine some components, or split some components, or have different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0061] The information interaction and execution process between the modules in the above-mentioned device are based on the same concept as the method embodiment of the present invention, and the specific details can be found in the description in the method embodiment of the present invention, and will not be repeated here.

[0062] This invention also provides an electronic device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements a method for evaluating broadband oscillations in a distributed power enrichment distribution network according to any embodiment of this invention.

[0063] This invention also provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program causes the processor to perform a broadband oscillation evaluation method for distributed power enrichment distribution networks according to any embodiment of this invention.

[0064] Specifically, a system or apparatus equipped with a storage medium may be provided, on which software program code implementing the functions of any of the embodiments described above is stored, and the computer (or CPU or MPU) of the system or apparatus may read and execute the program code stored in the storage medium.

[0065] In this case, the program code read from the storage medium can itself implement the function of any of the above embodiments, and therefore the program code and the storage medium storing the program code constitute part of the present invention.

[0066] Storage media embodiments for providing program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer via a communication network.

[0067] Furthermore, it should be clear that not only can the program code read by the computer be executed, but also the operating system or other components operating on the computer can be instructed based on the program code to perform some or all of the actual operations, thereby realizing the function of any of the embodiments described above.

[0068] Furthermore, it is understood that the program code read from the storage medium is written to the memory set in the expansion board inserted into the computer or to the memory set in the expansion module connected to the computer. Then, based on the instructions of the program code, the CPU or other components installed on the expansion board or expansion module execute some and all of the actual operations, thereby realizing the function of any of the above embodiments.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating broadband oscillations in a distributed generation-rich distribution network, characterized in that, include: S1. Obtain the basic parameters of the distribution network, and perform topological layering of the distribution network according to voltage level, and output the layered node association matrix; S2, based on the hierarchical node association matrix, the distributed power sources and loads in the distribution network are respectively constructed as port Norton models with controlled current sources, and the lines are constructed as π-type equivalent models. Through admittance merging, branch equivalent transformation and intermediate node elimination, the equivalent Norton model of the distribution network common connection point is obtained. S3, the frequency oscillation range of the distribution network is divided into multiple frequency bands. For each frequency band, the following steps are performed: the initial stability margin of the distribution network under that frequency band is calculated based on the equivalent admittance of the point of common coupling and the Thevenin impedance of the upstream grid, according to the equivalent Norton model; the stability margin includes phase margin and amplitude margin; the source-load coupling strength is determined based on the load equivalent admittance and the equivalent admittance of the point of common coupling, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin under that frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. S4. For each operating condition of the distribution network, repeat the process of determining the oscillation risk level in step S3 to determine the safe operating boundary of the distribution network based on the critical operating conditions that meet the preset safety level.

2. The method according to claim 1, characterized in that, The basic parameters of the distribution network include: distributed generation parameters, load parameters and load fluctuation characteristics, line parameters, transformer parameters, short-circuit impedance of the upstream grid, and voltage level parameters; the voltage level includes the low-voltage substation level, feeder level, and collection station level.

3. The method according to claim 1, characterized in that, The equivalent Norton model is: In the formula, for Equivalent admittance at the moment of common connection point; for Time of the first Equivalent admittance of a distributed power source For the number of distributed power sources, for Equivalent admittance of the current collector network at any time for Equivalent admittance at any given time.

4. The method according to claim 1, characterized in that, The source-load coupling strength is determined based on the following formula: Based on the aforementioned source-load coupling strength, the initial stability margin is corrected using the following formula: In the formula, for Source-load coupling strength at any given time; for Momentary load equivalent admittance; for Equivalent admittance at the moment of common connection point; and They are respectively Initial phase margin and initial gain margin at time t; and They are respectively The final phase margin and final magnitude margin at each time step.

5. The method according to claim 4, characterized in that, The determination of the oscillation risk level for this frequency band based on the final stability margin and the source-load coupling strength includes: Set differentiated risk thresholds, including initial phase warning threshold, initial phase high-risk threshold, amplitude warning threshold, and amplitude high-risk threshold; Determine whether the source-load coupling strength is greater than a preset coupling strength threshold. If not, use the initial phase warning threshold as the final phase warning threshold and the initial phase high-risk threshold as the final phase high-risk threshold. If yes, increase both the initial phase warning threshold and the initial phase high-risk threshold by a preset angle to obtain the final phase warning threshold and the final phase high-risk threshold. Based on the numerical relationship between the final phase margin, the final phase warning threshold, and the final phase high-risk threshold, the phase risk level of the distribution network is determined. The amplitude risk level of the distribution network is determined based on the numerical relationship between the final amplitude margin, the amplitude warning threshold, and the amplitude high-risk threshold. The higher of the phase risk level and the amplitude risk level is taken as the oscillation risk level of the distribution network in this frequency band.

6. The method according to claim 1, characterized in that, When the oscillation risk level exceeds the preset safety level, the following method is used to conduct source tracing analysis of the distribution network: Calculate the participation factor of each node in the hierarchical node association matrix, and designate nodes with participation factors greater than a set threshold as core nodes; Calculate the total impedance of all devices at all core nodes; For each device in the power distribution network, the device contribution is calculated based on the participation factor of its corresponding node, port impedance, and the total impedance. The device that contributes the most to the overall oscillation is designated as the core oscillation device. Increase the inverter damping coefficient of the core oscillation device to ensure that the adjusted damping coefficient meets the low-risk requirements of wideband oscillation.

7. The method according to claim 1, characterized in that, Determining the safe operating boundary of the power distribution network includes: The range of variation in distributed power penetration, load fluctuation, and source-load coupling strength is discretized into multiple combined operating conditions. Determine the oscillation risk level of each operating condition combination in each frequency band; Search for critical combination working conditions that satisfy the preset safety level in at least one working condition dimension; The maximum allowable installed capacity of distributed power sources, the allowable load fluctuation range, the minimum energy storage capacity, and the allowable source-load coupling strength range are determined based on the critical combination operating conditions.

8. A wideband oscillation assessment device for distributed power source enrichment distribution networks, characterized in that, include: The acquisition unit is used to acquire the basic parameters of the distribution network, perform topological layering of the distribution network according to voltage level, and output the layered node association matrix; The construction unit is used to construct the distributed power sources and loads in the distribution network as port Norton models with controlled current sources and the lines as π-type equivalent models based on the hierarchical node association matrix. The equivalent Norton model of the distribution network common connection point is obtained by admittance merging, branch equivalent transformation and intermediate node elimination. The evaluation unit is used to divide the frequency oscillation range of the distribution network into multiple frequency bands, and for each frequency band, performs the following: Based on the equivalent admittance at the point of common coupling and the Thevenin impedance of the upstream power grid, the initial stability margin of the distribution network in this frequency band is calculated; the stability margin includes phase margin and magnitude margin. The source-load coupling strength is determined based on the load equivalent admittance and the common connection point equivalent admittance, and the initial stability margin is corrected based on the source-load coupling strength to obtain the final stability margin in this frequency band. Based on the final stability margin and the source-load coupling strength, the oscillation risk level of this frequency band is determined, and when the oscillation risk level is greater than the preset safety level, a source tracing analysis is performed on the distribution network. The boundary determination unit is used to repeatedly execute the oscillation risk level determination process in the evaluation unit for each operating condition of the distribution network, so as to determine the safe operating boundary of the distribution network based on the critical operating condition that meets the preset safety level.

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