Method and system for controlling sending end of extra-high voltage direct current system

Abstract

The invention discloses a method and a system for controlling a sending end of an extra-high voltage direct current system, which are applied to the field of extra-high voltage direct current systems, and the method comprises the following steps: obtaining receiving end measurement data of the extra-high voltage direct current system; processing the receiving end measurement data to obtain a first data set; determining a plurality of second sub-data sets by taking the static voltage stability margin as a standard; constructing a simulation reference power flow model based on each second sub-data set; aiming at each simulation reference power flow model, adopting a continuous power flow method to obtain receiving end power limit data corresponding to each simulation reference power flow model; analyzing and processing the power limit data of each receiving end to obtain a power analysis result; and controlling the sending end of the extra-high voltage direct current system to execute the sending end power control strategy. According to the control method and system for the sending end of the extra-high voltage direct current system, the accuracy of receiving end voltage stability analysis and power limit calculation is improved, and then a reliable basis is provided for making a sending end control strategy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of UHVDC system, in particular to a control method and system for the sending end of UHVDC system. BACKGROUND

[0002] The UHVDC transmission system has the ability of super-long distance and super-large capacity power transmission, effectively solves the problem of long distance mislocation between energy center and load center, and has low transmission loss and good economy.

[0003] In the prior art, when analyzing and controlling the UHVDC transmission system, the receiving end in the UHVDC transmission system is often directly treated as a constant active load, and the value of the active load is usually directly taken as the planned value or rated value of the DC power, which leads to a serious deviation of the analysis result from the actual situation, and the voltage stability problem cannot be reflected, so that the potential voltage instability risk cannot be accurately identified by the analysis personnel. The operation mode and control strategy formulated based on such distorted analysis will seriously threaten the safety of the UHVDC system, not only may exacerbate the voltage collapse risk during system disturbance, but also may cause continuous commutation failure or even serious consequences such as blocking of the DC system during power grid fault, and finally leads to interruption of the operation of the entire UHVDC transmission system. SUMMARY

[0004] The present application provides a control method and system for the sending end of UHVDC system to solve the technical problem of inaccurate modeling of the receiving end in the UHVDC transmission system in the prior art, to accurately depict the operating characteristics of the receiving end power grid of the UHVDC system, improve the accuracy of voltage stability analysis and power limit calculation of the receiving end, and further provide a reliable basis for the formulation of the sending end control strategy, and ensure the safe and stable operation of the entire DC transmission system.

[0005] To solve the above technical problems, the present application provides a control method and system for the sending end of UHVDC system, the method comprising: obtaining the receiving end measurement data of the UHVDC system; processing the receiving end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving end measurement data to obtain a first data set; processing the sub-data set extracted from the first data set in the determined time period according to the preset static voltage stability margin as the standard to determine a plurality of second sub-data sets; constructing a simulation reference power flow model based on each second sub-data set, wherein the simulation reference power flow model designs the converter station node connected to the receiving end in the UHVDC system as an equivalent load with inner and outer loop control; For each of the aforementioned simulation reference power flow models, the continuous power flow method is adopted, and the active power of the equivalent load is used as the growth parameter of the simulation reference power flow model to solve for the receiving-end power limit data corresponding to each of the aforementioned simulation reference power flow models. The power limit data of each receiving end is analyzed and processed to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. The sending end of the ultra-high voltage direct current system is controlled to execute the sending end power control strategy determined by the power analysis results.

[0006] Preferably, the step of processing the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset includes: The receiving end measurement data is smoothed and filtered to obtain the receiving end filtered data; Based on the difference calculation result between the received-end filtered data and the received-end measurement data, the measurement residual value is obtained; The receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution are replaced with the corresponding receiving-end filtered data to obtain the first dataset.

[0007] Preferably, the step of processing a subset of data extracted from the first dataset within a defined time period, based on a preset static voltage stability margin, to determine several second subsets, including: Based on the power requirements of ultra-high voltage direct current transmission, the data acquisition time periods at different power levels at the receiving end are determined. Based on the quality assessment results of the measurement data for each power level, each determined time period is obtained by filtering from the corresponding data acquisition time period; The sub-dataset extracted from the first dataset within the determined time period is processed to obtain the static voltage stability margin of the sub-dataset; Based on the preset static voltage stability margin, several second subsets of data are determined.

[0008] Preferably, the step of constructing a simulation baseline power flow model based on each of the second subsets of data, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end of the UHVDC system as equivalent loads under inner and outer loop control, including: Extract the electrical parameters of the receiving end and the regulation parameter data of the converter station node from the second subset of data; The inner and outer loop control characteristics of the converter station node are obtained by analyzing the adjustment parameter data. Based on the electrical parameters and the inner and outer loop control characteristics, the equivalent load of the converter station node is determined; Based on the obtained topology and electrical parameters of the UHVDC system, an initial power flow model is constructed; The equivalent load is embedded into the initial power flow model to obtain the simulation baseline power flow model.

[0009] Preferably, the continuous power flow method is used for each of the simulation reference power flow models, and the active power of the equivalent load is used as the growth parameter of the simulation reference power flow model for solution, to obtain the receiving-end power limit data corresponding to each of the simulation reference power flow models, including: The active power of the equivalent load is used as the growth parameter of the simulation baseline power flow model, and the growth parameter is increased by a fixed step size as the growth rule of the simulation baseline power flow model. Based on the growth parameters and the growth rules, the continuous power flow method is used to solve the simulation benchmark power flow model to obtain a series of power flow solutions; The series of power flow solutions are screened and analyzed to obtain the receiving-end power limit data.

[0010] In another aspect, the present invention provides a control system for the sending end of an ultra-high voltage direct current system, comprising: The acquisition module is used to acquire the receiving-end measurement data of the UHVDC system; The residual module is used to process the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset; The processing module is used to process the subset of data extracted from the first dataset within a defined time period based on a preset static voltage stability margin, and to determine several second subsets of data. A construction module is used to construct a simulation baseline power flow model based on each of the second subset datasets, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end in the UHVDC system as equivalent loads controlled by inner and outer loops; The solution module is used to apply the continuous power flow method to each of the simulation reference power flow models, using the active power of the equivalent load as the growth parameter of the simulation reference power flow model to obtain the receiving-end power limit data corresponding to each of the simulation reference power flow models. The analysis module is used to analyze and process the power limit data of each receiving end to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. The execution module is used to control the sending end of the UHVDC system to execute the sending end power control strategy determined by the power analysis results.

[0011] Preferably, the residual module includes: The filtering unit is used to smooth and filter the receiving end measurement data to obtain receiving end filtered data. The residual value unit is used to calculate the measurement residual value based on the difference between the received-end filtered data and the received-end measurement data. The replacement unit is used to replace the receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution with the corresponding receiving-end filtered data to obtain the first dataset.

[0012] Preferably, the processing module includes: The determination unit is used to determine the data acquisition time periods at different power levels at the receiving end based on the power requirements of UHVDC transmission. An evaluation unit is used to select each determined time period from the corresponding data acquisition time period based on the quality evaluation results of the measurement data for each power level. A calculation unit is used to perform calculation processing on the subset of data extracted from the first dataset within a determined time period to obtain the static voltage stability margin of the subset of data. A reference unit is used to determine several second subsets of data based on a preset static voltage stability margin.

[0013] Preferably, the building module includes: An extraction unit is used to extract electrical parameters of the receiving end and adjustment parameter data of the converter station node from the second subset of data. The analysis unit is used to analyze the adjustment parameter data to obtain the inner and outer loop control characteristics of the converter station node; The determining unit is used to determine the equivalent load of the converter station node based on the electrical parameters and the inner and outer loop control characteristics; The power flow model unit is used to construct an initial power flow model based on the obtained topology and electrical parameters of the UHVDC system. The simulation baseline power flow model unit is used to embed the equivalent load into the initial power flow model to obtain the simulation baseline power flow model.

[0014] Preferably, the solution module includes: The growth unit is used to use the active power of the equivalent load as the growth parameter of the simulation reference power flow model, and to increase the growth parameter by a fixed step size as the growth rule of the simulation reference power flow model. The power flow solution unit is used to solve the simulation benchmark power flow model based on the growth parameters and the growth rules using the continuous power flow method to obtain a series of power flow solutions; The analysis unit is used to filter and analyze the series of power flow solutions to obtain the receiving-end power limit data.

[0015] Compared with the prior art, the beneficial effects of the present invention are at least one of the following: This scheme first acquires measurement data from the receiving end of the UHVDC system. It then analyzes the distribution of measurement residuals between node voltage and branch power flow to obtain the first dataset. Next, it extracts a subset of the first dataset over a defined time period and calculates the static voltage stability margin to determine the second subset. Based on this second subset, it constructs a simulation benchmark power flow model with the receiving-end converter station nodes designed as equivalent loads under inner and outer loop control. Using the continuous power flow method with the equivalent load active power as the growth parameter, it solves the model to obtain the receiving-end power limit data. This data is then analyzed to obtain power analysis results under different static voltage stability margins. Finally, it controls the sending end to execute the corresponding power control strategy. This scheme, through multi-stage data processing and model construction, accurately grasps the receiving-end grid stability margin and power limit, ensuring that the sending-end power control closely matches the receiving-end carrying capacity. This avoids both excessive power leading to receiving-end instability and insufficient power causing energy waste. Simultaneously, relying on dynamic analysis and precise control, it ensures the overall safety and stability of the system operation. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the control method of the sending end of an ultra-high voltage direct current system in one embodiment of the present invention; Figure 2 This is a schematic diagram of the control system at the sending end of an ultra-high voltage direct current system in one embodiment of the present invention; Figure label: The module consists of: 11. Acquisition module; 12. Residual module; 13. Processing module; 14. Construction module; 15. Solving module; 16. Analysis module; and 17. Execution module. Detailed Implementation

[0017] 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 only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Therefore, they should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] Ultra-high voltage direct current (UHVDC) transmission systems have advantages such as ultra-long distance and ultra-large capacity power transmission, which can effectively solve the problem of misalignment between energy and load centers, and have low losses.

[0022] However, when analyzing and controlling the system using existing technologies, the receiving end is often simplified to a constant active load, which leads to analysis results that are out of touch with reality, fail to reflect voltage stability issues, and are difficult to identify potential voltage instability risks. The operating modes and control strategies formulated based on this distorted analysis will seriously threaten system safety, may exacerbate the risk of voltage collapse, and may even cause DC system commutation failure and blockage, ultimately leading to the interruption of the entire power transmission system.

[0023] One embodiment of the present invention provides a control method for the sending end of an ultra-high voltage direct current system. For details, please refer to [link to relevant documentation]. Figure 1 , Figure 1 The diagram shown is a flowchart illustrating a control method for the sending end of an ultra-high voltage direct current system according to one embodiment of the present invention. The method includes: S1. Obtain the receiving-end measurement data of the UHVDC system; S2. Process the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset; S3. Using the preset static voltage stability margin as the standard, process the subset of data extracted from the first dataset within a defined time period to determine several second subsets. S4. Construct a simulation baseline power flow model based on each second subset of data. In the simulation baseline power flow model, the converter station nodes connected to the receiving end in the UHVDC system are designed as equivalent loads under inner and outer loop control. S5. For each simulation reference power flow model, the continuous power flow method is used, and the active power of the equivalent load is used as the growth parameter of the simulation reference power flow model to solve for the receiving end power limit data corresponding to each simulation reference power flow model. S6. Analyze and process the power limit data of each receiving end to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. S7. Control the sending end of the UHVDC system to execute the sending end power control strategy determined by the power analysis results.

[0024] In ultra-high voltage direct current (UHVDC) systems, the control of the sending end must be based on the actual state of the receiving end. As the power receiving and absorbing end, the voltage stability margin and power limit of the receiving end directly determine the power range that the sending end can transmit. Analyzing the receiving end can accurately grasp its carrying capacity and stability boundary. By extracting the measurement data of the receiving end to build a model and solving for the power limit, the reasonable range of power control at the sending end can be clarified, ensuring that the output power of the sending end meets the needs of the receiving end without exceeding its stability limit, thereby achieving safe and stable operation of the system. Therefore, this scheme models and analyzes the receiving end of the UHVDC system.

[0025] In step S1, acquiring measurement data from the receiving end of the UHVDC system addresses the problem of simplistic and distorted receiving-end models in existing technologies. This provides a realistic operational basis for subsequent accurate construction of the receiving-end model, analysis of voltage stability, and formulation of reliable control strategies. A lack of realistic measurement data can lead to unrealistic receiving-end model parameters, distorted voltage stability analysis results, and consequently, safety hazards in control strategies. This is primarily achieved through real-time measurement equipment deployed in the receiving-end power grid, collecting data from the converter station and surrounding key nodes to ensure data real-time performance and accuracy. Specifically, the acquired data includes AC side voltage, current, and phase angle at the converter station's access nodes; active power transmitted and reactive power consumed by the converter station; and power data from ordinary loads and power flow data from key branches in the surrounding area of ​​the receiving-end power grid. This step provides raw parameter support for constructing an equivalent load model that considers the internal and external loop control characteristics of the converter station, ensuring the model reflects the actual operating characteristics of the receiving end. It also guarantees the accuracy of subsequent static voltage stability margin calculations and receiving-end power limit analysis, helping analysts accurately identify potential voltage instability risks. Ultimately, this can provide a reliable basis for formulating control strategies at the sending end of the UHVDC system, reduce the probability of voltage collapse during system disturbances and converter failure or blocking during faults, and ensure the safe and stable operation of the entire power transmission system.

[0026] After acquiring the receiving-end measurement data, the data is preprocessed and smoothed by filtering to obtain the receiving-end filtered data. The measurement residual value is obtained based on the difference between the receiving-end filtered data and the receiving-end measurement data. The receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution is replaced with the corresponding receiving-end filtered data to obtain the first dataset. In the specific implementation of receiving-end measurement data processing, the original measurement data is first smoothed using either a moving average filter or a Kalman filter algorithm. If a moving average filter is used, a reasonable sliding window size must be determined first, usually based on the data sampling frequency and system disturbance characteristics, such as selecting 5-10 sampling periods as the window length. Then, the receiving-end filtered data at the corresponding time is generated by calculating the mean of the data within the window to reduce random noise and instantaneous fluctuations caused by sensor errors and electromagnetic interference. Subsequently, the difference between the receiving-end filtered data and the original receiving-end measurement data is calculated according to the time-by-time correspondence principle to obtain the measurement residual values ​​at each time. Next, the Shapiro-Wilk test or Kolmogorov-Smirnov test is used to perform a normality test on all measurement residual values. The time corresponding to the residual values ​​that do not conform to the normal distribution and the original measurement data are statistically analyzed. Finally, the original receiving-end measurement data corresponding to these residual values ​​that do not conform to the normal distribution are replaced one by one with the receiving-end filtered data obtained by smoothing at the same time, thus forming the first dataset.

[0027] Smoothing filtering is performed on the receiving-end measurement data. The core principle is to reduce random noise and instantaneous fluctuations caused by sensor errors and electromagnetic interference through filtering algorithms, while preserving the core trend of data changes with system operating conditions. This generates receiving-end filtered data that more closely reflects the actual operating conditions of the receiving end. Next, the difference between the receiving-end filtered data and the original receiving-end measurement data is calculated to obtain the measurement residual value. The magnitude of this residual value directly reflects the degree to which the original measurement data deviates from the true trend. Under normal circumstances, the measurement residual should follow a normal distribution around zero. If the residual value deviates from this distribution, it indicates that the corresponding original data may have anomalies. Based on this characteristic, measurement residual values ​​that do not conform to a normal distribution are selected, and the original receiving-end measurement data corresponding to these residual values ​​are replaced with the previously obtained receiving-end filtered data, ultimately forming the first dataset. By eliminating irrelevant interference through smoothing filtering and accurately identifying and correcting outliers in the original data through residual distribution testing, noise or abnormal data can be avoided from interfering with subsequent static voltage stability margin calculations and simulation baseline power flow model construction. This ensures that the subsequent analysis process can be carried out based on high-quality and high-reliability data, thereby improving the accuracy of the power analysis results and sending-end control strategies of the entire UHVDC system.

[0028] In step S3, using a preset static voltage stability margin as a standard, the subsets extracted from the first dataset within a defined time period are processed to determine several second subsets. Based on the UHVDC transmission power demand, the data acquisition time periods at different power levels at the receiving end are determined. Based on the measurement data quality assessment results for each power level, specific time periods are selected from the corresponding data acquisition time periods. The subsets extracted from the first dataset within the defined time periods are processed to obtain the static voltage stability margin of the subsets. Using the preset static voltage stability margin as a benchmark, several second subsets are determined. By accurately selecting second subsets from the initial first dataset that meet the UHVDC transmission power demand, have acceptable data quality, and satisfy static voltage stability requirements, a reliable basis is provided for subsequent power grid simulation modeling and power control strategy formulation. The implementation involves three steps: First, determine the data acquisition time period. Identify common transmission power levels in UHVDC systems, such as 60%, 80%, and 100% of rated power. Then, based on the typical operating time and load variation patterns of each power level, set corresponding continuous data acquisition periods for each power level. For example, collect 24 hours or 12 hours of measurement data for each level to ensure the data reflects the true operating characteristics of the receiving-end power grid at different power levels. Second, screen the determined time periods and conduct quality assessments on the measurement data within each power level's acquisition period. This involves checking whether the data integrity reaches a preset threshold of 95% or higher. The process involves three steps: First, determining if the data fluctuation range is within a reasonable range; second, eliminating invalid periods with high data loss rates or severe noise interference, and retaining only the quality-compliant periods as the final data set; and third, calculating the static voltage stability margin and determining the second subset of data. This subset is formed by extracting key parameters such as node voltage, branch power, and load power within the defined time period from the first dataset. Then, using the continuous power flow method, with load power increasing proportionally, the power difference between the current operating point and the voltage collapse point is calculated. This difference represents the static voltage stability margin of the subset. Finally, the calculated margin is compared with a preset standard, and the subset that meets the standard is selected as the final second subset. This approach ensures that the acquired second subset matches actual power demand, guarantees data quality, and meets voltage stability requirements. It avoids deviations in stability margin calculations due to unreasonable data periods or poor data quality, thereby ensuring the accuracy of subsequent power grid simulation models and the safety and stability of the UHVDC system.

[0029] In step S3, a simulation baseline power flow model is constructed based on each second subset of the dataset. This model designs the converter station nodes connected to the receiving end of the UHVDC system as equivalent loads with inner and outer loop control. Electrical parameters of the receiving end and regulation parameters of the converter station nodes are extracted from the second subset of the dataset. The regulation parameter data are analyzed to obtain the inner and outer loop control characteristics of the converter station nodes. Based on the electrical parameters and inner and outer loop control characteristics, the equivalent load of the converter station nodes is determined. An initial power flow model is constructed based on the obtained topology and electrical parameters of the UHVDC system. The equivalent load is then embedded into the initial power flow model to obtain the simulation baseline power flow model. The electrical parameters of the receiving-end power grid and the regulation parameters of at least one converter station are extracted from the second subset of the dataset because the electrical parameters of the receiving-end power grid reflect the grid topology and basic operating conditions, while the regulation parameters of the converter stations reflect their control logic characteristics. Together, they provide core data support for subsequent modeling. During implementation, the electrical parameters of the receiving-end power grid to be extracted are first defined, including node voltage amplitude and phase angle, branch resistance and reactance, and active and reactive power of the load. The regulation parameters of the converter stations include inner-loop current control settings, outer-loop power control reference values, and voltage control dead zone range. Then, corresponding parameter data are selected from the second subset of the dataset according to time series or steady-state operating points. The regulation parameter data is analyzed to obtain the inner and outer loop control characteristics of the converter stations because the complex control logic of the converter stations needs to be transformed into characteristic patterns that the model can recognize. During implementation, the outer-loop power control response coefficient is determined by analyzing the relationship between the current setting value and the power reference value in the regulation parameter data, and the inner-loop voltage regulation sensitivity is determined by the parameter fluctuations within the voltage control dead zone range. This allows for the summarization of the dynamic response characteristics and steady-state regulation patterns of the inner and outer loop control. Based on the receiving-end electrical parameters and the inner and outer loop control characteristics, the model is then developed. The equivalent load of the converter station is used to transform this special component into a load model that meets the requirements of power flow calculation. During implementation, based on the voltage and power demand of the converter station's access node in the receiving-end electrical parameters, and combined with the power regulation range and response speed in the inner and outer loop control characteristics, the active and reactive power values ​​of the equivalent load are calculated to ensure that the equivalent load reflects the actual power consumption and regulation capacity of the converter station. The initial power flow model is constructed based on the obtained topology and electrical parameters of the receiving-end power grid to build a basic calculation model that conforms to the actual structure of the receiving-end power grid. During implementation, the node and branch connection diagram is first drawn in the power flow calculation software according to the receiving-end power grid topology, and then the node load and branch impedance data from the receiving-end electrical parameters are entered into the model to complete the parameter settings of the initial power flow model. Embedding the equivalent load into the initial power flow model to obtain the simulation benchmark power flow model is to improve the model's simulation of the converter station component. During implementation, the converter station access node is found in the initial power flow model, and the determined equivalent load data replaces the original load parameters of that node, completing the equivalent load embedding operation. Finally, a simulation benchmark power flow model that can be used for subsequent power limit calculations is formed.The advantage of doing this is that by extracting key parameters, analyzing control characteristics, and determining equivalent loads, the role of the converter station in the receiving-end power grid can be accurately simulated, and a simulation benchmark power flow model that fits the actual operating conditions can be constructed. This provides a reliable model basis for solving the receiving-end power limit using the continuous power flow method, avoids deviations in power limit calculations due to inaccurate converter station modeling, and thus ensures the rationality and safety of the power control strategy at the sending end of the UHVDC system.

[0030] In practical systems, there are various scenarios involving source load power and DC power. Theoretically, the simulation should use the source load power and DC power at the same moment, the latter of which can be obtained from the DC transmission power plan. The active power PdR transmitted at the DC sending end of an UHV system has a piecewise relationship with the source load power, namely: In the formula: Ps is the total power of the AC system source load; Pbase represents the power of the UHVDC system receiving end source load in the most typical scenario; P1, P2, and P3 correspond to the planned values ​​of the active power of the UHVDC system sending end when the load range is at its peak, middle, and valley, respectively.

[0031] After obtaining the simulation baseline power flow model, the active power of the equivalent load is used as the growth parameter of the simulation baseline power flow model, and the growth rule of the growth parameter is increased by a fixed step size. Based on the growth parameter and the growth rule, the continuous power flow method is used to solve the simulation baseline power flow model to obtain a series of power flow solutions. The series of power flow solutions are screened and analyzed to obtain the receiving-end power limit data. The active power of the equivalent load model is used as the growth parameter of the simulation baseline power flow model because the equivalent load can accurately reflect the actual power demand and regulation characteristics of the converter station. Its active power change directly corresponds to the power carrying pressure change of the receiving end grid. The growth of this parameter can simulate the actual scenario of the receiving end power gradually increasing. The growth rule of increasing the growth parameter with a fixed step size is determined to ensure that the power growth process is controllable and the calculation results are stable, and to avoid the omission of key stability nodes due to the step size being too large or the increase of redundant calculation due to the step size being too small. In implementation, a fixed step size is first set according to the power range and calculation accuracy requirements of the simulation baseline power flow model. For example, the step size value is determined by 2% to 5% of the initial active power of the equivalent load. The active power of the equivalent load is increased by this step size in each calculation. The continuous power flow method is used to solve the simulated baseline power flow model based on growth parameters and growth rules to obtain a series of power flow solutions. This is because the continuous power flow method can overcome the convergence problem of traditional power flow methods when approaching the stability limit, and accurately track the entire process of the power grid from steady state to voltage collapse. In implementation, the simulated baseline power flow model is first imported into the continuous power flow calculation module, the equivalent load active power is set as the growth variable and a fixed step size parameter is entered. After the calculation is started, the software will gradually increase the equivalent load active power according to the step size. Each time it is increased, the power flow equation is solved once, and a series of power flow solutions including parameters such as the voltage amplitude, phase angle and branch power flow of each node are obtained until the calculation fails to converge, that is, it stops when it is close to the voltage collapse point. The process of filtering and analyzing a series of power flow solutions to obtain the receiving-end power limit data is necessary because it is essential to extract key values ​​reflecting the stability boundary of the power grid from a large amount of calculation results. In practice, the process begins by screening the moments in the series of power flow solutions when node voltages begin to drop significantly or branch power flows approach their limits. The equivalent load active power value corresponding to these moments is recorded. Then, interpolation calculations are performed using power flow solution data from adjacent steps to further refine the power value corresponding to the stability limit. The final determined power value is the receiving-end power limit data. By rationally selecting growth parameters and rules, and combining the advantages of the continuous power flow method, the receiving-end power growth process can be systematically and accurately simulated, obtaining comprehensive power flow change data. This allows for the accurate extraction of the receiving-end power limit, providing a reliable basis for subsequent analysis of the power carrying capacity of the UHVDC system under different stability margins, and effectively ensuring the safety and rationality of the sending-end power control strategy.

[0032] The power limit data for each receiving end is analyzed and processed to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. Analyzing and processing the power limit data for each receiving end to obtain the power analysis results under the corresponding static voltage stability margin is necessary because the receiving end power limit data only reflects the upper limit of power carrying capacity in a single dimension. Combining this with the static voltage stability margin allows for the establishment of a correspondence between stability capability and power limit, clarifying the power range that the system can withstand under different stability levels, and providing a more comprehensive decision-making basis for sending-end control. In implementation, each receiving end power limit data is first correlated one-to-one with the static voltage stability margin corresponding to the simulation baseline power flow model that generated the data, forming a data pair of stability margin and power limit. Then, the mean and deviation are calculated for multiple power limit data within the same stability margin range, and values ​​exceeding the reasonable fluctuation range are eliminated. The analysis process involves identifying outliers within the dynamic range, followed by an analysis of the power limit variation trends under different stability margins. For example, it determines whether the power limit increases linearly or non-linearly as the stability margin increases. Simultaneously, it explains the underlying reasons for the trends by considering the receiving-end grid topology and load distribution characteristics. For instance, if a region experiences high load density leading to a decrease in stability margin, the power limit may decrease synchronously. Next, the analysis quantifies the power limit safety redundancy corresponding to different stability margins, calculating the difference and ratio between the current operating power and the power limit to determine the adjustable power range at the sending end under each stability margin. Finally, it integrates the correlation results, trend analysis, and safety redundancy data to form a power analysis result that includes the stability margin level, the corresponding power limit value, and the recommended power adjustment range. The advantage of this approach is that it transforms isolated power limit data into a systematic analysis conclusion deeply bound to the stability margin, clearly presenting the power carrying capacity and safety boundaries of the UHVDC system under different stability states. This avoids the risks that may arise from formulating sending-end control strategies based solely on a single power limit value, ensuring that sending-end power adjustment meets both receiving-end needs and grid stability characteristics, further enhancing the safety of system operation.

[0033] The sending end of the UHVDC system is controlled to implement a power control strategy determined by power analysis results. This strategy is crucial because the power analysis clearly defines the power limits and safe adjustment ranges of the receiving-end grid under different static voltage stability margins. As the power output end, the sending end must match the receiving end's carrying capacity based on these results to avoid excessive power output leading to grid instability or excessive power output causing energy waste, thus ensuring the safe and economical operation of the system. During implementation, the stability margin level, corresponding power limit value, and suggested power adjustment range from the power analysis results are first imported into the decision module of the sending-end control system. The system first identifies the current static voltage stability margin level of the receiving-end grid, then retrieves the suggested power adjustment range for that level, and, combined with the current power generation output and equipment operating status of the sending end, determines the specific power control target. For example, if the current stability margin is at a high level and the upper limit of the adjustment range has not reached the power limit, the sending-end power can be increased to a reasonable value within the range. If the stability margin is low, the power needs to be reduced to a safe range. Subsequently, the sending-end control system changes the DC output power of the sending-end converter station by adjusting the converter valve trigger angle or modulation pulse width. During the process, the actual output value of the sending-end power and the operating status data fed back by the receiving end are collected in real time and compared with the control target value. If there is a deviation, the control parameters are dynamically corrected through the proportional-integral-derivative adjustment algorithm to ensure that the sending-end power operates stably within the target range. At the same time, overload protection and emergency load shedding trigger conditions are set. When a sudden failure at the receiving end causes a sharp drop in the stability margin, the sending end can quickly reduce the output power according to the preset protection logic to avoid system cascading failures. The advantage of this approach is that it allows the sending-end power control to closely match the actual stability and carrying capacity of the receiving-end power grid. This avoids the risk of voltage collapse that may be caused by blindly increasing power, while making full use of the stability margin of the receiving-end power grid to achieve efficient energy transmission. At the same time, through real-time feedback adjustment and fault protection mechanisms, it ensures the stability, safety, and economy of the overall operation of the UHVDC system, and guarantees that power transmission continuously meets the power demand of the receiving end.

[0034] Another embodiment of the present invention provides a control system for the sending end of an ultra-high voltage direct current system. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 The diagram shown illustrates the structure of a control system at the sending end of an ultra-high voltage direct current (UHVDC) system according to one embodiment of the present invention. The system includes: Module 11 is used to acquire the receiving-end measurement data of the UHVDC system; The residual module 12 is used to process the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset; Processing module 13 is used to process a subset of data extracted from the first dataset within a defined time period based on a preset static voltage stability margin, and to determine several second subsets of data. Module 14 is used to build a simulation baseline power flow model based on each second subset of data, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end in the UHVDC system as equivalent loads controlled by inner and outer loops. The solver module 15 is used to solve for each simulation reference power flow model using the continuous power flow method, with the active power of the equivalent load as the growth parameter of the simulation reference power flow model, to obtain the receiving-end power limit data corresponding to each simulation reference power flow model. Analysis module 16 is used to analyze and process the power limit data of each receiving end to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. The execution module 17 is used to control the sending end of the UHVDC system to execute the sending end power control strategy determined by the power analysis results.

[0035] Preferably, the residual module 12 includes: The filtering unit is used to smooth and filter the measurement data at the receiving end to obtain filtered data at the receiving end. The residual value unit is used to calculate the measurement residual value based on the difference between the received-end filtered data and the received-end measurement data. The replacement unit is used to replace the receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution with the corresponding receiving-end filtered data to obtain the first dataset.

[0036] Preferably, the processing module 13 includes: The determination unit is used to determine the data acquisition time periods at different power levels at the receiving end based on the power requirements of UHVDC transmission. The evaluation unit is used to select specific time periods from the corresponding data acquisition time periods based on the quality evaluation results of the measurement data for each power level. The calculation unit is used to perform calculations on a subset of data extracted from the first dataset within a defined time period to obtain the static voltage stability margin of the subset of data. The reference unit is used to determine several second subsets of data based on a preset static voltage stability margin.

[0037] Preferably, the building module 14 includes: The extraction unit is used to extract electrical parameters of the receiving end and regulation parameter data of the converter station nodes from the second subset of data. The analysis unit is used to analyze the adjustment parameter data to obtain the inner and outer loop control characteristics of the converter station nodes; The determination unit is used to determine the equivalent load of the converter station nodes based on electrical parameters and inner and outer loop control characteristics; The power flow model unit is used to construct an initial power flow model based on the obtained topology and electrical parameters of the UHVDC system. The simulation baseline power flow model unit is used to embed the equivalent load into the initial power flow model to obtain the simulation baseline power flow model.

[0038] Preferably, the solver module 15 includes: The growth unit is used to use the active power of the equivalent load as the growth parameter of the simulation baseline power flow model, and to use the growth parameter with a fixed step size as the growth rule of the simulation baseline power flow model. The power flow solution unit is used to solve the simulation benchmark power flow model based on the growth parameters and growth rules using the continuous power flow method, and obtain a series of power flow solutions; The analysis unit is used to filter and analyze a series of power flow solutions to obtain the receiving-end power limit data.

[0039] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0040] Accordingly, embodiments of the present invention provide a computer-readable storage medium, the computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform steps in the control method of the ultra-high voltage direct current system sending end as described in the above embodiments, for example... Figure 1 Steps S1 to S7 as described above.

[0041] This invention first collects measurement data from the receiving end of an ultra-high voltage direct current (UHVDC) system, processes the data by combining the measurement residual distributions of node voltage and branch power flow, and generates a first dataset. Then, it extracts subsets within a defined time period from the first dataset, calculates the static voltage stability margin of each subset, and uses this to select a second subset. Next, it constructs a simulation benchmark power flow model based on the second subset, where the receiving-end converter station nodes are equivalent to loads with inner and outer loop control characteristics. A continuous power flow method is then used, with the active power of the equivalent load as an increasing parameter to solve the model and obtain the receiving-end power limit data. Subsequently, the power limit data is analyzed to obtain power analysis results corresponding to different static voltage stability margins. Finally, based on these results, the sending end is controlled to execute corresponding power control strategies. Its beneficial effects are reflected in the fact that through multi-step data optimization and model building, the stability boundary and power carrying capacity of the receiving-end power grid are accurately grasped, ensuring that the sending-end power output meets the safe operation requirements of the receiving end while fully utilizing energy. Through dynamic analysis and precise control, the safety and stability of the UHVDC system operation are effectively guaranteed.

[0042] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A control method for the sending end of an ultra-high voltage direct current (UHVDC) system, characterized in that, include: Acquire measurement data at the receiving end of the ultra-high voltage direct current system; The receiving-end measurement data is processed based on the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset; Using a preset static voltage stability margin as a standard, the subset of data extracted from the first dataset within a defined time period is processed to determine several second subsets of data. A simulation baseline power flow model is constructed based on each of the second subset datasets, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end in the UHVDC system as equivalent loads controlled by inner and outer loops; For each of the aforementioned simulation reference power flow models, the continuous power flow method is adopted, and the active power of the equivalent load is used as the growth parameter of the simulation reference power flow model to solve for the receiving-end power limit data corresponding to each of the aforementioned simulation reference power flow models. The power limit data of each receiving end is analyzed and processed to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. The sending end of the ultra-high voltage direct current system is controlled to execute the sending end power control strategy determined by the power analysis results.

2. The control method for the sending end of an ultra-high voltage direct current system as described in claim 1, characterized in that, The first dataset is obtained by processing the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data, including: The receiving end measurement data is smoothed and filtered to obtain the receiving end filtered data; Based on the difference calculation result between the received-end filtered data and the received-end measurement data, the measurement residual value is obtained; The receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution are replaced with the corresponding receiving-end filtered data to obtain the first dataset.

3. The control method for the sending end of an ultra-high voltage direct current system as described in claim 1, characterized in that, The process involves processing a subset of data extracted from the first dataset within a defined time period, based on a preset static voltage stability margin, to determine several second subsets of data, including: Based on the power requirements of ultra-high voltage direct current transmission, the data acquisition time periods at different power levels at the receiving end are determined. Based on the quality assessment results of the measurement data for each power level, each determined time period is obtained by filtering from the corresponding data acquisition time period; The sub-dataset extracted from the first dataset within the determined time period is processed to obtain the static voltage stability margin of the sub-dataset; Based on the preset static voltage stability margin, several second subsets of data are determined.

4. The control method for the sending end of an ultra-high voltage direct current system as described in claim 1, characterized in that, The simulation baseline power flow model is constructed based on each of the second subset datasets, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end of the UHVDC system as equivalent loads under inner and outer loop control, including: Extract the electrical parameters of the receiving end and the regulation parameter data of the converter station node from the second subset of data; The inner and outer loop control characteristics of the converter station node are obtained by analyzing the adjustment parameter data. Based on the electrical parameters and the inner and outer loop control characteristics, the equivalent load of the converter station node is determined; Based on the obtained topology and electrical parameters of the UHVDC system, an initial power flow model is constructed; The equivalent load is embedded into the initial power flow model to obtain the simulation baseline power flow model.

5. The control method for the sending end of an ultra-high voltage direct current system as described in claim 1, characterized in that, The continuous power flow method is used for each of the simulation reference power flow models, and the active power of the equivalent load is used as the growth parameter of the simulation reference power flow model for solution, to obtain the receiving-end power limit data corresponding to each simulation reference power flow model, including: The active power of the equivalent load is used as the growth parameter of the simulation baseline power flow model, and the growth parameter is increased by a fixed step size as the growth rule of the simulation baseline power flow model. Based on the growth parameters and the growth rules, the continuous power flow method is used to solve the simulation benchmark power flow model to obtain a series of power flow solutions; The series of power flow solutions are screened and analyzed to obtain the receiving-end power limit data.

6. A control system for the sending end of an ultra-high voltage direct current system, characterized in that, include: The acquisition module is used to acquire the receiving-end measurement data of the UHVDC system; The residual module is used to process the receiving-end measurement data according to the measurement residual distribution of node voltage and branch power flow in the receiving-end measurement data to obtain the first dataset; The processing module is used to process the subset of data extracted from the first dataset within a defined time period based on a preset static voltage stability margin, and to determine several second subsets of data. A construction module is used to construct a simulation baseline power flow model based on each of the second subset datasets, wherein the simulation baseline power flow model designs the converter station nodes connected to the receiving end in the UHVDC system as equivalent loads controlled by inner and outer loops; The solution module is used to apply the continuous power flow method to each of the simulation reference power flow models, using the active power of the equivalent load as the growth parameter of the simulation reference power flow model to obtain the receiving-end power limit data corresponding to each of the simulation reference power flow models. The analysis module is used to analyze and process the power limit data of each receiving end to obtain the power analysis results of the UHVDC system under the corresponding static voltage stability margin. The execution module is used to control the sending end of the UHVDC system to execute the sending end power control strategy determined by the power analysis results.

7. The control system at the sending end of the ultra-high voltage direct current system as described in claim 6, characterized in that, The residual module includes: The filtering unit is used to smooth and filter the receiving end measurement data to obtain receiving end filtered data. The residual value unit is used to calculate the measurement residual value based on the difference between the received-end filtered data and the received-end measurement data. The replacement unit is used to replace the receiving-end measurement data corresponding to the measurement residual values ​​that do not conform to the normal distribution with the corresponding receiving-end filtered data to obtain the first dataset.

8. The control system at the sending end of the ultra-high voltage direct current system as described in claim 6, characterized in that, The processing module includes: The determination unit is used to determine the data acquisition time periods at different power levels at the receiving end based on the power requirements of UHVDC transmission. An evaluation unit is used to select each determined time period from the corresponding data acquisition time period based on the quality evaluation results of the measurement data for each power level. A calculation unit is used to perform calculation processing on the subset of data extracted from the first dataset within a determined time period to obtain the static voltage stability margin of the subset of data. A reference unit is used to determine several second subsets of data based on a preset static voltage stability margin.

9. The control system at the sending end of the ultra-high voltage direct current system as described in claim 6, characterized in that, The building module includes: An extraction unit is used to extract electrical parameters of the receiving end and adjustment parameter data of the converter station node from the second subset of data. The analysis unit is used to analyze the adjustment parameter data to obtain the inner and outer loop control characteristics of the converter station node; The determining unit is used to determine the equivalent load of the converter station node based on the electrical parameters and the inner and outer loop control characteristics; The power flow model unit is used to construct an initial power flow model based on the obtained topology and electrical parameters of the UHVDC system. The simulation baseline power flow model unit is used to embed the equivalent load into the initial power flow model to obtain the simulation baseline power flow model.

10. The control system at the sending end of the ultra-high voltage direct current system as described in claim 6, characterized in that, The solution module includes: The growth unit is used to use the active power of the equivalent load as the growth parameter of the simulation reference power flow model, and to increase the growth parameter by a fixed step size as the growth rule of the simulation reference power flow model. The power flow solution unit is used to solve the simulation benchmark power flow model based on the growth parameters and the growth rules using the continuous power flow method to obtain a series of power flow solutions; The analysis unit is used to filter and analyze the series of power flow solutions to obtain the receiving-end power limit data.

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