A power system voltage optimization control method based on digital twinning

Abstract

The application belongs to the technical field of power systems, and provides a power system voltage optimization control method based on digital twinning, which comprises the following steps: acquiring independent voltage constraint ranges of a main grid and a distribution grid, constructing a transformer ratio correlation model, and acquiring main grid compatible voltage subranges and distribution grid compatible voltage subranges; simulating dynamic operation conditions through the construction of a digital twinning model, and outputting main-distribution grid dynamic voltage ranges through simulation analysis; wherein the main-distribution grid dynamic voltage ranges comprise main grid dynamic voltage ranges and distribution grid dynamic voltage ranges; the method optimizes the problem of effect cancellation caused by blind adjustment, ensures that the distribution grid performs limited coordinated adjustment when the main grid is given priority, and the main grid synchronously assists adjustment when the distribution grid is given priority, and resolves the contradiction between main grid voltage reduction and distribution grid voltage increase.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically a power system voltage optimization control method based on digital twins. Background Technology

[0002] Voltage in a power system is a core parameter for the transmission, distribution, and use of electrical energy. It directly determines the stability of the system and the safety of electrical equipment. To ensure the safety of equipment, voltage must be continuously maintained, which requires hierarchical regulation of the main grid (transmission network) and distribution network in the power system.

[0003] However, voltage fluctuations in the main grid (transmission network) (such as the start-up and shutdown of large generating units and adjustments to regional tie lines) are transmitted to the distribution network through transformers; the reactive power regulation of distributed generation (DG) in the distribution network will in turn affect the voltage of the main grid. The main grid usually focuses on regional voltage stability (such as maintaining the voltage of the 500kV / 220kV bus within the rated range) and tie line power balance (such as the planned execution of inter-provincial power transmission). In order to reduce the voltage of the main grid, measures such as "reducing the reactive power output of generators and switching capacitors" may be taken. However, there may be conflicts between the control objectives of the main grid and the distribution network, and there is a lack of coordination mechanism between the two control objectives.

[0004] For example, the main grid needs to reduce voltage (e.g., the 110kV bus voltage needs to be reduced from 118kV to 110kV), while the distribution network needs to generate capacitive reactive power from DG due to high local voltage (further pushing up the main grid voltage). The two control directions are opposite, which causes the main grid control measures (such as switching capacitors) to be offset by the reactive power regulation of the distribution network DG. The voltage cannot be effectively controlled, and may even aggravate fluctuations, which may lead to equipment overload, protection malfunction and system stability risks.

[0005] Therefore, this invention provides a power system voltage optimization control method based on digital twins. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by this invention to solve its technical problem is: a power system voltage optimization control method based on digital twins, comprising the following steps:

[0008] Obtain the independent voltage constraint ranges of the main grid and distribution network, and construct a transformer ratio correlation model to obtain the compatible voltage sub-ranges of the main grid and the compatible voltage sub-ranges of the distribution network;

[0009] By constructing a digital twin model, dynamic operating conditions are simulated, and the dynamic voltage range of the main distribution network is output through simulation analysis.

[0010] The dynamic voltage range of the main grid and distribution grid includes: the dynamic voltage range of the main grid and the dynamic voltage range of the distribution grid.

[0011] The dynamic voltage range of the main and distribution networks corresponding to different dynamic operating conditions is compared with the voltage sub-range of the main network and the voltage sub-range of the distribution network to identify the variation deviation. The operating conditions with large variation deviations are extracted as key monitoring conditions.

[0012] Based on key monitoring conditions, real-time monitoring data of the main grid and distribution network are obtained to identify whether the voltage deviation is caused by a conflict with control objectives.

[0013] If there is a conflict in the control objectives, the adjustment priorities of the main grid and the distribution network are determined, and the adjustment amounts of the main grid and the distribution network are calculated based on the adjustment priorities and the direction of coordinated control, and the control strategy is executed.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention addresses the problem of offsetting measures caused by opposite adjustment directions in the main grid and distribution network. It first screens for conflicts by comparing control targets, then uses a transfer coefficient to calculate the mutual influence of adjustments to verify the actual conflict. Simultaneously, it calculates a priority coefficient using a weighted average of deviation ratio and abnormal coverage ratio to determine the adjustment sequence, and corrects the actual adjustment amount based on passive voltage changes. This optimizes the problem of offsetting effects caused by blind adjustments, ensuring that the distribution network performs limited coordinated adjustments when the main grid has priority, and that the main grid synchronously assists in adjustments when the distribution network has priority, thus resolving the contradiction of mutual obstruction between main grid voltage reduction and distribution network voltage increase.

[0016] This invention quickly identifies high-risk scenarios through a key monitoring mechanism, reducing the waste of resources in full-area monitoring. Data-driven priority determination and adjustment calculation not only ensure voltage stability and power balance in the main grid area and protect distribution network user-side equipment from over / under voltage damage, but also reduce the risk of accidents such as equipment overload and protection malfunction, thereby improving the operating efficiency of the power system. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a flowchart of the steps of a power system voltage optimization control method based on digital twins according to the present invention;

[0019] Figure 2 This is a logic flowchart of step S50 in a power system voltage optimization control method based on digital twins according to the present invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] Example

[0022] Please see Figure 1 and Figure 2 As shown in the embodiment of the present invention, a power system voltage optimization control method based on digital twin includes the following steps:

[0023] Step S10: Obtain the independent voltage constraint ranges of the main grid and the distribution network, and construct the transformer ratio correlation model to obtain the compatible voltage sub-ranges of the main grid and the compatible voltage sub-ranges of the distribution network;

[0024] In this step, the independent voltage constraint ranges of the main grid and the distribution network are obtained;

[0025] The independent voltage constraint range of the main grid is determined by those skilled in the art by referring to national power industry standards (such as GB / T12325-2023 "Power Quality Supply Voltage Permissible Deviation"), clarifying the rated voltage and permissible fluctuation range of each level of the main grid bus, and obtaining the independent voltage constraint range of each voltage level bus of the main grid.

[0026] The independent voltage constraint range of the distribution network shall be determined by those skilled in the art in accordance with industry standards (such as DL / T 1564-2016 "Technical Guidelines for Distribution Network Planning and Design"), to clarify the voltage constraints of the distribution network nodes and obtain the independent voltage constraint range of each voltage level node in the distribution network.

[0027] The specific process of constructing the transformer turns ratio correlation model is as follows:

[0028] Obtain basic transformer parameters and real-time operating parameters;

[0029] The basic parameters of a transformer include, but are not limited to: rated turns ratio (i.e., the ratio of the rated voltage on the high-voltage side to the rated voltage on the low-voltage side), and adjustable tap range (e.g., ±5%, with an adjustment step of 1.25% per tap, corresponding to a tap coefficient range of 0.95-1.05).

[0030] Real-time operating parameters include, but are not limited to: real-time voltage on the transformer main grid side (high voltage side), real-time voltage on the distribution network side (low voltage side), and the coefficient corresponding to the current tap position (e.g., if the current tap position is +2.5%, then the corresponding coefficient is 1.025).

[0031] The transformer turns ratio correlation model can be formed through forward mapping calculation and reverse mapping verification and calibration.

[0032] The specific process of forward mapping is as follows: taking the rated transformation ratio of the transformer as the benchmark, the real-time voltage on the main grid side is multiplied with the rated transformation ratio to calculate the theoretical distribution network side voltage;

[0033] Based on the current tap position of the transformer and the corresponding tap coefficient, the theoretical distribution network side voltage is calculated by comparing it with the correction coefficient to obtain the corrected distribution network side voltage.

[0034] Based on this, historical operating data is introduced for error compensation. Scenario data similar to the current operating conditions are extracted from the past 6 months (similarity refers to: same tap position, similar main grid voltage fluctuation range). The deviation values ​​between the corrected distribution network side voltage and the real-time distribution network side voltage for these operating conditions are recorded and calculated.

[0035] Among them, the main grid voltage fluctuation range is close to the difference between the current main grid voltage and the historical main grid voltage, which is less than or equal to ±1kV; the number of similar scenario data sets should be greater than or equal to 30 sets. If there are less than 30 sets, the main grid voltage fluctuation range should be expanded to less than or equal to ±2kV and then re-screened.

[0036] Calculate the mean of all deviation values ​​as the compensation coefficient, add the corrected distribution network side voltage to the compensation coefficient, and obtain the calculated distribution network side voltage.

[0037] The specific process of reverse mapping is as follows: Starting with the real-time voltage on the distribution network side, subtract the compensation coefficient to obtain the corrected distribution network side voltage.

[0038] The theoretical distribution network side voltage is obtained by multiplying the corrected distribution network side voltage by the tap factor.

[0039] Divide the theoretical distribution network voltage by the rated transformer ratio to deduce the calculated main grid voltage.

[0040] Verify whether the results of forward mapping and reverse mapping are consistent, that is, whether the main grid side calculated voltage finally deduced by reverse mapping is consistent with the main grid side real-time voltage initially input by forward mapping;

[0041] If the results of the forward mapping and the reverse mapping are consistent, then the transformer turns ratio correlation model is formed, specifically as follows:

[0042] Input parameters: Real-time voltage on the main grid side, rated transformer ratio, current tap changer coefficient, and compensation coefficient for the corresponding operating condition (obtained from historical data statistics);

[0043] Core mapping formula:

[0044] Distribution network side calculated voltage = (main grid side real-time voltage × rated transformer ratio / tap changer coefficient) + compensation coefficient;

[0045] Model constraints: The compensation coefficients need to be stored in groups according to "tap coefficient + main grid voltage range" (e.g., establish a two-dimensional reference table: tap coefficient 1.025, main grid voltage 108-112kV, corresponding compensation coefficient +0.16kV) so that the corresponding coefficients can be called under different operating conditions;

[0046] Output results: When the real-time voltage of the main grid is given, the calculated voltage of the distribution network is output; when the real-time voltage of the distribution network is given, the calculated voltage of the main grid is output through the reverse formula, and the results are consistent in both directions.

[0047] If the results of forward mapping and reverse mapping are inconsistent, the root cause of the positioning deviation (such as poor adaptability of compensation coefficients, incorrect tap coefficients, or insufficient matching degree of historical data) is to correct the corresponding parameters and re-execute forward and reverse mapping until the results are consistent.

[0048] Based on the completed transformer ratio correlation model, the specific process for obtaining the main grid compatible voltage sub-range and the distribution network compatible voltage sub-range is as follows:

[0049] Traverse the discrete node voltage values ​​within the independent voltage constraint range of the main grid (e.g., one node per 0.1kV zone), calculate the corresponding distribution network voltage value through the transformer ratio correlation model, and select the main grid voltage range where the distribution network voltage value falls within the independent voltage constraint range of the distribution network as the main grid compatible voltage sub-range;

[0050] Similarly, by iterating through the discrete node voltage values ​​within the independent voltage constraint range of the distribution network, the corresponding main grid voltage value is inversely derived through the transformer ratio correlation model, and the distribution network voltage range in which the main grid voltage value falls within the independent voltage constraint range of the main grid is selected as the distribution network compatible voltage sub-range.

[0051] Among them, the compatibility voltage range of the main grid and distribution network includes the compatibility voltage sub-range of the main grid and the compatibility voltage sub-range of the distribution network;

[0052] Among them, the main and distribution network compatible voltage range can simultaneously meet the independent constraints of the main network and the distribution network and conform to the transformer ratio correlation characteristics of the main and distribution network cooperative compatible voltage range.

[0053] For example, the compatibility range of the 110kV busbar in the main grid is [108kV, 110kV], and the compatibility range of the 10kV feeder in the distribution network is [10.3kV, 10.5kV]).

[0054] Step S20: Simulate the dynamic operating conditions by constructing a digital twin model, and output the dynamic voltage range of the main distribution network through simulation analysis;

[0055] The dynamic voltage range of the main grid and distribution grid includes: the dynamic voltage range of the main grid and the dynamic voltage range of the distribution grid.

[0056] In this step, the process of constructing the digital twin model is as follows: using the design parameters, historical operating data, and real-time monitoring data of the power system's physical entity as input, the model is constructed using a combination of parameter mapping and mechanism modeling.

[0057] Parameter mapping: The physical parameters of equipment such as generators (rated voltage 10.5kV, maximum active power output 600MW), transmission lines (model LGJ-400, resistance 0.08Ω / km, reactance 0.4Ω / km), and distribution transformers (capacity 500kVA, transformation ratio 10kV / 0.4kV, short-circuit impedance 4%) are synchronized in real time from the SCADA system (sampling frequency 1Hz) to the digital twin platform (such as AVEVA Digital Twin) via the OPCUA protocol.

[0058] Mechanism modeling: The main grid layer uses the node admittance matrix to describe the topological relationship, the distribution network layer uses a three-phase power flow model (considering the load three-phase imbalance degree ≤5%), and the correlation layer establishes the coupling relationship through the transformer ratio formula (the ratio of the voltage on the main grid side to the voltage on the distribution network side). The model solution is implemented using the Power System Blockset module of MATLAB / Simulink.

[0059] Model validation: Select 72 consecutive hours of historical operating data (including 2000 sets of main grid voltage and distribution network load data), compare the simulated voltage values ​​output by the model with the measured values ​​of the physical system, and the error must be ≤2% (calculated as the ratio of the absolute value of the difference between the simulated value and the measured value to the measured value). If the error is not met, optimize parameters such as line resistance and load characteristic curves through particle swarm optimization until the standard is met, such as optimizing the temperature compensation coefficient of line resistance and the dynamic correction factor of the power factor of the load characteristic curve.

[0060] In this step, the simulation process is as follows: simulate typical dynamic operating conditions, including but not limited to: large unit start-up and shutdown, regional tie line power adjustment, DG reactive power output fluctuation, load peak and valley changes, and post-fault recovery.

[0061] For example, dynamic operating condition 1 (large load fluctuation): the residential load suddenly increases by 30% from the baseline value (5000kW) (lasting for 15 minutes), and the industrial load (including 60% of the motor load) drops by 20% (lasting for 10 minutes).

[0062] Dynamic operating condition 2 (DG output fluctuation): The output of the photovoltaic power station (installed capacity 10MW) drops from 8MW to 2MW due to cloud cover (completed within 3 minutes), and the output of the wind power (installed capacity 5MW) fluctuates randomly within ±2MW (frequency 0.1Hz).

[0063] Dynamic operating condition 3 (main grid operation): 220kV line reclosing operation (fault clearing time 0.08 seconds, reclosing time 0.5 seconds), main transformer tap changer adjustment (adjustment step size 1.25%, response time 2 seconds);

[0064] Input the main grid compatible voltage sub-range (e.g., 220kV bus: [210kV, 230kV]) and the distribution network compatible voltage sub-range (e.g., 10kV feeder: [9.3kV, 10.7kV]) as constraints;

[0065] The improved Newton-Raphson method (iteration accuracy 1e-6, maximum number of iterations 20) was used to solve the node voltage under various dynamic operating conditions. The voltage values ​​of each bus in the main network and each node in the distribution network were recorded every 0.1 seconds.

[0066] The voltage transfer coefficients on both sides of the transformer (the ratio of the voltage change on the main grid side to the voltage change on the distribution network side, corresponding to the dynamic operating conditions) are calculated using the correlation layer model (the transformer ratio correlation model in step S10 above).

[0067] This transfer coefficient is used to quantify the coupling strength between the main grid and the distribution grid voltage fluctuations, verify the rationality of the main grid and distribution grid voltage interaction in the simulation scenario, and provide a basis for the coupling law for the extraction of extreme values ​​in the dynamic voltage range.

[0068] For each simulation scenario under dynamic operating conditions, the extreme values ​​and durations of voltage fluctuations are extracted to form a structured output of the main grid dynamic voltage range and the distribution network dynamic voltage range.

[0069] Main grid dynamic voltage range: recorded in the format of "voltage level + node number + [minimum value, maximum value] + duration";

[0070] For example, “220kV#M102: [208kV, 232kV], lasting 8 minutes”;

[0071] Distribution network dynamic voltage range: recorded in the format of "feeder number + [minimum value, maximum value] + out-of-tolerance duration";

[0072] For example, “10kV#F301: [9.1kV, 10.9kV], out of tolerance for 2 minutes”;

[0073] Output data is stored in a real-time database (such as InfluxDB) and can be accessed in JSON format.

[0074] Step S30: Identify the variation deviations between the dynamic voltage range of the main grid and the compatible voltage sub-range of the main grid and the compatible voltage sub-range of the distribution network corresponding to different dynamic operating conditions, and extract the operating conditions with large variation deviations as key monitoring conditions;

[0075] In this step, based on any dynamic operating condition, the compatible voltage range of the main grid and distribution network is obtained, including the compatible voltage sub-range of the main grid and the compatible voltage sub-range of the distribution network.

[0076] Obtain the dynamic range of the main grid and the dynamic range of the distribution network;

[0077] The difference between the minimum value of the main grid dynamic range and the minimum value of the main grid compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the minimum value of the main grid.

[0078] The difference between the minimum value of the dynamic range of the distribution network and the minimum value of the compatible voltage sub-range of the distribution network is calculated, and the absolute value is taken to obtain the degree of change of the minimum value of the distribution network.

[0079] The difference between the maximum value of the main grid dynamic range and the maximum value of the main grid compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the maximum value of the main grid.

[0080] The difference between the maximum value of the distribution network dynamic range and the maximum value of the distribution network compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the maximum value of the distribution network.

[0081] The sum of the duration for which the main grid dynamic voltage exceeds the main grid compatible voltage sub-range and the duration for which the distribution network dynamic voltage exceeds the distribution network compatible voltage sub-range is obtained as the comprehensive excess duration.

[0082] Extract the maximum value between the minimum and maximum values ​​of the main grid voltage variation, and use it as the maximum deviation of the main grid voltage.

[0083] Extract the maximum value between the minimum and maximum value of the distribution network voltage variation as the maximum voltage deviation of the distribution network.

[0084] If any one of the following conditions is met: the maximum deviation of the main grid voltage is greater than the threshold of the maximum deviation of the main grid voltage, the maximum deviation of the distribution network voltage is greater than the threshold of the maximum deviation of the distribution network voltage, or the comprehensive deviation duration is greater than the threshold of the comprehensive deviation duration, then the dynamic operating condition is determined to be a key monitoring condition.

[0085] If it does not exist, then the dynamic operating condition is determined to be a non-key monitoring condition.

[0086] Among them, the maximum deviation threshold of the main grid voltage, the maximum deviation threshold of the distribution network voltage, and the comprehensive deviation duration threshold are set by those skilled in the art based on the voltage quality standards of the power industry and actual operating experience.

[0087] Step S40: Based on key monitoring conditions, acquire real-time monitoring data of the main grid and distribution network, and identify whether the voltage deviation is caused by a conflict with control targets;

[0088] In this step, real-time monitoring data of the main grid and distribution network is acquired. The monitoring data includes: operating status parameters of the main grid and distribution network and control command parameters.

[0089] The operating status parameters of the main grid and distribution network include: the voltage of each busbar in the main grid (such as the real-time voltage values ​​of the 220kV and 110kV buses); generator operating parameters (active power output and reactive power output); transmission line parameters (line power); and main transformer operating parameters (real-time voltage on the main grid side and the coefficient corresponding to the current tap position).

[0090] Distribution network node / feeder voltages (e.g., real-time voltage values ​​of 10kV feeders and 0.4kV distribution areas); Distributed generation (DG) operating parameters (active power output and reactive power output); Distribution network load parameters (real-time power of residential / industrial loads);

[0091] Operating parameters of distribution transformers (real-time voltage on the distribution network side, coefficient corresponding to the current tap position);

[0092] The control command parameters for the main grid and distribution network include: control commands issued by the main grid dispatching system (such as generator reactive power adjustment commands and main transformer tap changer adjustment commands); and control commands issued by the distribution network automation system (such as DG reactive power adjustment commands).

[0093] In this step, the process of identifying whether the voltage deviation is caused by a conflict with the control target is as follows:

[0094] Compare the voltage of each busbar in the main grid with the voltage range of the main grid compatible sub-grids;

[0095] If the real-time voltage of the main grid bus is higher than the upper limit of the main grid compatible voltage sub-range, the main grid control target is determined to be voltage reduction; if the real-time voltage of the main grid bus is lower than the lower limit of the main grid compatible voltage sub-range, the main grid control target is determined to be voltage increase.

[0096] Determine the range of main grid regulation requirements by combining the maximum deviation of the main grid voltage;

[0097] Compare the voltage range of distribution network nodes / feeders to the distribution network's compatible voltage range;

[0098] If the real-time voltage of the distribution network feeder is higher than the upper limit of the distribution network's compatible voltage sub-range, the distribution network control objective is determined to be voltage reduction; if the real-time voltage of the distribution network feeder is lower than the lower limit of the distribution network's compatible voltage sub-range, the distribution network control objective is determined to be voltage increase.

[0099] The range of distribution network regulation needs is determined by combining the maximum deviation of the distribution network voltage.

[0100] If the control objectives of the main grid and the distribution network are completely opposite, it is preliminarily determined that there is a conflict in control direction;

[0101] The completely opposite control objectives mean that the distribution network needs to increase voltage when the main network needs to reduce voltage, or the distribution network needs to reduce voltage when the main network needs to increase voltage.

[0102] If both control objectives are the same (e.g., both require voltage reduction) or if one of the voltages has no adjustment requirement within the compatibility range, then control direction conflict is ruled out, and the investigation proceeds to non-conflict cause troubleshooting.

[0103] Based on the initial determination of a control direction conflict, the voltage transfer coefficients (the ratio of the voltage change on the main grid side to the voltage change on the distribution network side) calculated in step S20 are invoked to quantify the mutual influence of the main grid and distribution network regulation measures:

[0104] Impact of main grid regulation on distribution network: If the main grid executes generator reactive power adjustment command or main transformer tap adjustment command, the change in voltage at distribution network nodes can be calculated by the voltage transfer coefficient on both sides of the transformer. For example, a 2kV reduction in the main grid voltage will result in a 0.2kV reduction in the distribution network voltage.

[0105] Impact of distribution network regulation on the main grid: If the distribution network executes the DG reactive power regulation command, the change in the main grid bus voltage caused by the regulation can be estimated by the voltage transfer coefficient on both sides of the transformer. For example, a 0.3kV increase in the distribution network voltage will lead to a 3kV increase in the main grid voltage simultaneously.

[0106] If the impact of the main grid regulation on the distribution network is opposite to the distribution network control objective, and the impact of the distribution network regulation on the main grid is opposite to the main grid control objective, then the voltage deviation is ultimately determined to be caused by a conflict of control objectives; otherwise, the voltage deviation is ultimately determined not to be caused by a conflict of control objectives.

[0107] It needs to be explained that the core characteristic of control target conflict is that the regulation measures of the main grid and the distribution grid hinder each other and form a reverse cancellation. That is, the regulation of the main grid will aggravate the voltage deviation of the distribution grid (opposite to the control target of the distribution grid), and the regulation of the distribution grid will also aggravate the voltage deviation of the main grid (opposite to the control target of the main grid). Only when both of these conditions are met can it be determined as a control target conflict.

[0108] For example, the main grid voltage reduction causes the distribution network voltage to fall further below the lower limit, which conflicts with the distribution network voltage increase target, and the distribution network voltage increase causes the main grid voltage to rise further above the upper limit, which conflicts with the main grid voltage reduction target.

[0109] Based on the final determination that the voltage deviation is not caused by a control target conflict, the causes of deviation that are not related to control target conflicts should be investigated, including but not limited to:

[0110] If the corresponding equipment parameters (such as generator reactive power output and DG reactive power output) do not change according to the command after the main grid / distribution network control command is issued, it is determined that the deviation is caused by equipment execution failure.

[0111] If the power of transmission lines and the load parameters of distribution networks suddenly increase or decrease (such as a sudden increase of 30% in load), and the main and distribution networks adjust in the same direction but the response is lagging, it is determined that the deviation is caused by a single dynamic disturbance that has not been calmed.

[0112] Step S50: If there is a conflict in control objectives, determine the adjustment priorities of the main grid and the distribution network, and calculate the adjustment amounts of the main grid and the distribution network based on the adjustment priorities and the direction of coordinated control, and execute the control strategy.

[0113] In this step, the process of determining the adjustment priorities of the main grid and distribution network based on two dimensions—voltage deviation and coverage of the affected area—is as follows:

[0114] Obtain the maximum deviation of the main grid voltage and calculate the ratio with the maximum deviation threshold of the main grid voltage to obtain the main grid deviation ratio;

[0115] Obtain the maximum deviation of the distribution network voltage and calculate the ratio with the maximum deviation threshold of the distribution network voltage to obtain the distribution network deviation ratio;

[0116] Calculate the abnormal coverage ratio of the main grid and the abnormal coverage ratio of the distribution network respectively;

[0117] The calculation process for the main grid abnormal coverage ratio is as follows: the proportion of the number of main grid buses with voltage deviations to the total number of main grid buses at the corresponding voltage level.

[0118] The calculation process for the distribution network abnormal coverage ratio is as follows: the proportion of the number of distribution network feeders with voltage deviations to the total number of distribution network feeders in the corresponding area;

[0119] Voltage deviation refers to a situation where the dynamic voltage value of the main grid or distribution network exceeds the compatible voltage sub-range of the main grid or the compatible voltage sub-range of the distribution network.

[0120] The main network deviation ratio and the main network abnormal coverage ratio are weighted and fused to output the main network priority coefficient.

[0121] The distribution network deviation ratio and the distribution network anomaly coverage ratio are weighted and fused to output the distribution network priority coefficient.

[0122] It should be noted that the weighting coefficients are allocated based on the principle of prioritizing risk intensity and secondarily on the breadth of impact, with the deviation ratio weighted at 0.6 and the anomaly coverage ratio weighted at 0.4.

[0123] The priority coefficient reflects the comprehensive risk level of voltage anomalies in the main grid or distribution network under control target conflict scenarios. The larger the coefficient value, the higher the instantaneous risk intensity and the risk of spread of the network, and the stronger the urgency of obtaining regulation resources (such as generator reactive capacity and DG regulation authority).

[0124] Main grid priority coefficient: quantifies the severity of the main grid voltage deviation from the safety benchmark and the superimposed risk of the abnormality affecting the bus. The larger the coefficient value, the greater the threat of the main grid voltage abnormality to the stability of the regional power grid (such as tie line power balance and large unit grid connection safety), and the more likely the main grid regulation command should be executed. Distribution network priority coefficient: quantifies the severity of the distribution network voltage deviation from the safety benchmark and the superimposed risk of the abnormality affecting the feeder. The larger the coefficient value, the more widespread the impact of the distribution network voltage abnormality on user-side equipment (such as residential appliances and industrial motors), and the more likely the distribution network regulation command should be executed.

[0125] If the priority coefficient of the main grid is greater than or equal to the priority coefficient of the distribution network, then the regulation priority of the main grid is higher.

[0126] If the priority coefficient of the main grid is less than that of the distribution network, then the regulation priority of the distribution network is higher.

[0127] When the priority coefficient of the main grid is equal to that of the distribution network, the stability of the main grid is prioritized, which can reduce the escalation of local anomalies into system failures.

[0128] In this step, the control strategy is executed based on the adjustment priority and the direction of coordinated control. The process is as follows:

[0129] If the main network adjustment has a high priority:

[0130] Obtain the main grid compatible voltage sub-range and the main grid dynamic range. Based on the maximum deviation of the main grid voltage (take the maximum value of the difference between the extreme value of the main grid dynamic range and the extreme value of the compatible voltage sub-range), determine the direction (boost or buck) of the main grid adjustment and the adjustment amount (the absolute value corresponding to the maximum deviation) to ensure that the main grid dynamic voltage range returns to the compatible sub-range.

[0131] By referring to the voltage transfer coefficients on both sides of the transformer, and combining this with the regulation amount and direction of the main grid, the passive voltage change in the distribution network is calculated:

[0132] When the main grid needs to be boosted, the passive voltage change in the distribution network is positive (synchronous passive boost).

[0133] When the main grid needs to be stepped down, the passive voltage change in the distribution network is negative (synchronous passive step-down).

[0134] The passive voltage change in the distribution network is the product of the regulation in the main network and the reciprocal of the voltage transfer coefficient on both sides of the transformer.

[0135] Obtain the distribution network compatible voltage sub-range and distribution network dynamic range. Based on the maximum deviation of the distribution network voltage (take the maximum value of the difference between the extreme value of the distribution network dynamic range and the extreme value of the compatible sub-range), determine the direction of adjustment required by the distribution network itself (positive for voltage boost and negative for voltage drop) and the original adjustment amount of the distribution network (the absolute value corresponding to the maximum deviation), and ensure that the distribution network dynamic voltage range returns to the compatible sub-range.

[0136] The actual coordinated adjustment amount of the distribution network (the actual coordinated adjustment amount of the distribution network) is calculated by: calculating the difference between the target voltage of the distribution network and the current dynamic range boundary of the distribution network, and then calculating the difference between the target voltage of the distribution network and the passive voltage change of the distribution network.

[0137] It should be explained that the target voltage of the distribution network is: the boundary value (lower limit or upper limit) of the distribution network's current dynamic range that is closest to the current dynamic range of the distribution network within the distribution network's compatible voltage sub-range; the boundary of the current dynamic range of the distribution network is: the boundary value corresponding to the target voltage within the distribution network's dynamic range (if the target voltage is the lower limit of compatibility, then the lower limit of the distribution network's dynamic range is taken; if it is the upper limit of compatibility, then the upper limit of the distribution network's dynamic range is taken).

[0138] Wherein, boost pressure is a positive value and deboost pressure is a negative value;

[0139] For example, if the main grid is compatible with the voltage range of 110kV bus [108kV, 110kV] (lower limit 108kV, upper limit 110kV);

[0140] Main grid dynamic range: 110kV bus [112kV, 113kV] (dynamic minimum 112kV, dynamic maximum 113kV);

[0141] The maximum deviation of the main grid voltage is 4kV; the control target is to reduce the maximum value of the dynamic voltage of the main grid from 113kV to 110kV and the minimum value from 112kV to 108kV, with the core regulation target being -4kV (voltage reduction).

[0142] The reciprocal of the voltage transfer coefficient across the transformer is 0.1, and the passive voltage change in the distribution network is -0.4kV (voltage reduction).

[0143] Distribution network compatible voltage range: 10kV feeder [10.3kV, 10.5kV] (lower limit 10.3kV, upper limit 10.5kV);

[0144] Distribution network dynamic range: 10kV feeder [9.8kV, 10.0kV] (dynamic minimum 9.8kV, dynamic maximum 10.0kV);

[0145] The maximum voltage deviation of the distribution network is +0.5kV (boost); the actual coordination adjustment to be performed by the distribution network is: 10.3kV-9.8kV-(-0.4kV)=10.3-9.8+0.4=0.1kV (boost).

[0146] The execution control strategies include, but are not limited to: core grid regulation methods: generator reactive power adjustment and main transformer tap changer auxiliary regulation;

[0147] Distribution network coordination and regulation methods: reactive power regulation of distributed generation (DG), switching of dynamic reactive power compensation devices and auxiliary regulation of distribution transformer taps.

[0148] If the distribution network has a high adjustment priority;

[0149] Obtain the distribution network compatible voltage sub-range and distribution network dynamic range. Based on the maximum deviation of the distribution network voltage (take the maximum value of the difference between the extreme value of the distribution network dynamic range and the extreme value of the compatible sub-range), determine the direction of adjustment (voltage increase or voltage decrease) and the amount of adjustment of the distribution network (the absolute value corresponding to the maximum deviation) to ensure that the distribution network dynamic voltage range returns to the compatible voltage sub-range.

[0150] By referring to the voltage transfer coefficients on both sides of the transformer, and combining the adjustment amount and direction of the distribution network, the passive voltage change of the main grid is calculated:

[0151] When the distribution network needs to be stepped up, the passive voltage change of the main network is positive (synchronous passive step-up).

[0152] When the distribution network needs to be stepped down, the passive voltage change in the main network is negative (synchronous passive step-down).

[0153] The passive voltage change in the main grid is the product of the regulation of the distribution network and the voltage transfer coefficient on both sides of the transformer.

[0154] Obtain the main grid compatible voltage sub-range and the main grid dynamic range. Based on the maximum deviation of the main grid voltage (take the maximum value of the difference between the extreme value of the main grid dynamic range and the extreme value of the compatible voltage sub-range), determine the direction of adjustment required by the main grid itself (positive for boost and negative for buck) and the original adjustment amount of the main grid (the absolute value corresponding to the maximum deviation), and ensure that the main grid dynamic voltage range returns to the compatible sub-range.

[0155] The actual auxiliary regulation amount of the main grid (the actual coordinated regulation amount of the main grid) is calculated by: calculating the difference between the target voltage of the main grid and the current dynamic range boundary of the main grid, and then calculating the difference between the target voltage of the main grid and the passive voltage change of the main grid.

[0156] It needs to be explained that the target voltage of the main grid is: the boundary value (lower limit or upper limit) of the main grid compatible voltage sub-range that is closest to the current dynamic range of the main grid; the boundary of the current dynamic range of the main grid is: the boundary value of the main grid dynamic range that corresponds to the target voltage (if the target voltage is the lower limit of compatibility, then the lower limit of the main grid dynamic range is taken; if it is the upper limit of voltage compatibility, then the upper limit of the main grid dynamic range is taken).

[0157] The control strategies implemented include, but are not limited to: core regulation methods for the distribution network: reactive power regulation of distributed power sources and switching of dynamic reactive power compensation devices; and auxiliary regulation methods implemented synchronously by the main grid: reactive power adjustment of generators and adjustment of main transformer taps, etc., to ensure that the distribution network returns to the compatibility range first and the main grid maintains stability synchronously.

[0158] This embodiment effectively optimizes the problems of voltage regulation cancellation and increased system fluctuation caused by control target conflicts between the main grid and distribution network in the existing power system through the design of digital twin modeling, dynamic deviation identification, conflict determination and priority collaborative control. It realizes the collaborative optimization control of the main grid and distribution network voltage, significantly improves the stability, voltage control accuracy and operating efficiency of the power system, and at the same time ensures the dual goals of main grid area stability and user-side equipment safety.

[0159] To address the issue of offsetting measures caused by opposite adjustment directions between the main grid and distribution network, a preliminary screening of conflicts is first conducted by comparing control targets. Then, the mutual influence of adjustments is calculated using the transfer coefficient to verify the actual conflicts. Simultaneously, priority coefficients are calculated by weighting deviation ratio and abnormal coverage ratio to determine the adjustment sequence. The actual adjustment amount is then corrected based on passive voltage changes, thus optimizing the problem of offsetting effects caused by blind adjustments. This ensures that when the main grid takes priority, the distribution network performs limited coordinated adjustments, and when the distribution network takes priority, the main grid performs synchronous auxiliary adjustments, resolving the contradiction of mutual obstruction between main grid voltage reduction and distribution network voltage increase.

[0160] By quickly identifying high-risk scenarios through a key monitoring mechanism, the waste of resources in full-area monitoring is reduced. Data-driven priority determination and adjustment calculation not only ensure voltage stability and power balance in the main grid area and tie line, but also ensure that distribution network user-side equipment is protected from over / under voltage damage. This can reduce the risk of accidents such as equipment overload and protection malfunction, and improve the operating efficiency of the power system.

[0161] By constructing a transformer turns ratio correlation model and digital twin dynamic simulation, the system can accurately map and quantify the bidirectional voltage of the main grid and distribution network, providing high-precision data support for coordinated control. It can also identify potential voltage deviation risks in advance by simulating various dynamic operating conditions. At the same time, through the dual judgment of control targets and priority coordination mechanism, it can optimize the problem of measures offsetting due to the opposite adjustment direction of the main grid and distribution network in the hierarchical control, and scientifically allocate regulation resources based on the intensity and scope of voltage deviation. Finally, through closed-loop control of the entire process, it can ensure the voltage stability of the main grid area and the power balance of the tie line, build a solid overall safety defense line for the power system, and ensure that the equipment on the user side of the distribution network is protected from overvoltage and undervoltage damage.

[0162] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A power system voltage optimization control method based on digital twin, characterized in that: Includes the following steps: Obtain the independent voltage constraint ranges of the main grid and distribution network, and construct a transformer ratio correlation model to obtain the compatible voltage sub-ranges of the main grid and the compatible voltage sub-ranges of the distribution network; By constructing a digital twin model, dynamic operating conditions are simulated, and the dynamic voltage range of the main distribution network is output through simulation analysis. The dynamic voltage range of the main grid and distribution grid includes: the dynamic voltage range of the main grid and the dynamic voltage range of the distribution grid. The dynamic voltage range of the main and distribution networks corresponding to different dynamic operating conditions is compared with the voltage sub-range of the main network and the voltage sub-range of the distribution network to identify the variation deviation. The operating conditions with large variation deviations are extracted as key monitoring conditions. Based on key monitoring conditions, real-time monitoring data of the main grid and distribution network are obtained to identify whether the voltage deviation is caused by a conflict with control objectives. The process of identifying whether the voltage deviation is caused by a conflict with control objectives includes: If a preliminary determination indicates a conflict in control direction, the voltage transfer coefficients on both sides of the transformer are used to quantify the mutual influence between the main grid and distribution network regulation measures. The impact of main grid regulation on distribution network: If the main grid executes generator reactive power adjustment command or main transformer tap adjustment command, the change in voltage at distribution network nodes caused by the regulation can be calculated by using the voltage transfer coefficient on both sides of the transformer. The impact of distribution network regulation on the main grid: If the distribution network executes the DG reactive power regulation command, the change in the main grid bus voltage caused by the regulation can be calculated by using the voltage transfer coefficient on both sides of the transformer. If the impact of the main grid regulation on the distribution network is opposite to the distribution network control objective, and the impact of the distribution network regulation on the main grid is opposite to the main grid control objective, then the voltage deviation is ultimately determined to be caused by a conflict in control objectives. If there is a conflict in the control objectives, the adjustment priorities of the main grid and the distribution network are determined, and the adjustment amounts of the main grid and the distribution network are calculated based on the adjustment priorities and the direction of coordinated control, and the control strategy is executed.

2. The power system voltage optimization control method based on digital twin according to claim 1, characterized in that: The process for obtaining the main grid compatible voltage sub-range and the distribution network compatible voltage sub-range is as follows: Traverse the discrete node voltage values ​​within the independent voltage constraint range of the main grid, calculate the corresponding distribution network voltage values ​​through the transformer ratio correlation model, and select the main grid voltage range where the distribution network voltage values ​​fall within the independent voltage constraint range of the distribution network as the main grid compatible voltage sub-range. By iterating through the discrete node voltage values ​​within the independent voltage constraint range of the distribution network, and using the transformer ratio correlation model to inversely deduce the corresponding main grid voltage value, the distribution network voltage range in which the main grid voltage value falls within the independent voltage constraint range of the main grid is selected as the distribution network compatible voltage sub-range.

3. The power system voltage optimization control method based on digital twin according to claim 1, characterized in that: The process of defining the output dynamic voltage range of the main distribution network is as follows: Input the main grid compatible voltage sub-range and the distribution network compatible voltage sub-range as constraints; The improved Newton-Raphson method was used to solve the node voltages under various dynamic operating conditions, and the voltage values ​​of each bus in the main network and each node in the distribution network were recorded. The voltage transfer coefficient across the transformer is calculated using a transformer turns ratio correlation model. The voltage transfer coefficient across the transformer is the ratio of the voltage change on the main grid side to the voltage change on the distribution network side. For each simulation scenario under dynamic operating conditions, the extreme values ​​of voltage fluctuations are extracted to output the dynamic voltage range of the main grid and the dynamic voltage range of the distribution network.

4. The power system voltage optimization control method based on digital twin according to claim 1, characterized in that: The process of acquiring the key monitoring conditions is as follows: The sum of the duration during which the main grid dynamic voltage exceeds the main grid compatible voltage sub-range and the duration during which the distribution network dynamic voltage exceeds the distribution network compatible sub-range is used as the comprehensive deviation duration. Obtain the maximum deviation of the main grid voltage and the maximum deviation of the distribution network voltage; If any one of the following three conditions is met—exceeding the maximum deviation of the main grid voltage, exceeding the maximum deviation of the distribution network voltage, or exceeding the overall deviation duration—then the dynamic operating condition is determined to be a key monitoring condition.

5. The power system voltage optimization control method based on digital twin according to claim 4, characterized in that: The process for obtaining the maximum deviation of the main grid voltage and the maximum deviation of the distribution network voltage is as follows: Based on any dynamic operating condition; The difference between the minimum value of the main grid dynamic range and the minimum value of the main grid compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the minimum value of the main grid. The difference between the minimum value of the dynamic range of the distribution network and the minimum value of the compatible voltage sub-range of the distribution network is calculated, and the absolute value is taken to obtain the degree of change of the minimum value of the distribution network. The difference between the maximum value of the main grid dynamic range and the maximum value of the main grid compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the maximum value of the main grid. The difference between the maximum value of the distribution network dynamic range and the maximum value of the distribution network compatible voltage sub-range is calculated, and the absolute value is taken to obtain the degree of change of the maximum value of the distribution network. Extract the maximum value between the minimum and maximum values ​​of the main grid voltage variation, and use it as the maximum deviation of the main grid voltage. Extract the maximum value between the minimum and maximum voltage variation of the distribution network as the maximum voltage deviation of the distribution network.

6. The power system voltage optimization control method based on digital twin according to claim 1, characterized in that: The process of initially determining that there is a control direction conflict includes: By comparing the voltage of each busbar in the main grid with the voltage sub-range compatible with the main grid, it can be determined whether the main grid control objective is to step down or step up. Determine the range of main grid regulation requirements by combining the maximum deviation of the main grid voltage; By comparing the voltage of distribution network nodes / feeders with the voltage sub-ranges compatible with the distribution network, it can be determined whether the control objective of the distribution network is to step down or step up. Determine the range of distribution network regulation requirements by combining the maximum voltage deviation of the distribution network; If the control objectives of the main grid and the distribution network are completely opposite, it is preliminarily determined that there is a conflict in control direction.

7. The power system voltage optimization control method based on digital twin according to claim 5, characterized in that: The process of determining the adjustment priorities of the main grid and the distribution network is as follows: The main grid deviation ratio is the ratio of the maximum deviation of the main grid voltage to the threshold value of the maximum deviation of the main grid voltage, while the distribution network deviation ratio is the ratio of the maximum deviation of the distribution network voltage to the threshold value of the maximum deviation of the distribution network voltage. The main grid anomaly coverage ratio is the proportion of the number of main grid buses with voltage deviations to the total number of main grid buses at the corresponding voltage level. The distribution network anomaly coverage ratio is the proportion of the number of distribution network feeders with voltage deviations to the total number of distribution network feeders in the corresponding area. Voltage deviation refers to a situation where the dynamic voltage value of the main grid or distribution network exceeds the compatible voltage sub-range of the main grid or the compatible voltage sub-range of the distribution network. The main network deviation ratio and the main network abnormal coverage ratio are combined to output the main network priority coefficient. The distribution network deviation ratio and the distribution network anomaly coverage ratio are integrated to output the distribution network priority coefficient. If the priority coefficient of the main grid is greater than or equal to the priority coefficient of the distribution network, then the regulation priority of the main grid is higher; otherwise, the regulation priority of the distribution network is higher.

8. The power system voltage optimization control method based on digital twin according to claim 5, characterized in that: Based on the adjustment priority and the direction of coordinated control, the adjustment quantities of the main grid and the distribution network are calculated. The process includes: If the main network adjustment has a high priority: The maximum deviation of the main grid voltage is used as the adjustment amount for the main grid; The product of the main grid regulation and the reciprocal of the voltage transfer coefficient on both sides of the transformer is used as the passive voltage change in the distribution network. Based on the maximum voltage deviation of the distribution network, determine the direction in which the distribution network itself needs to be adjusted. The difference between the target voltage of the distribution network and the current dynamic range boundary of the distribution network is calculated, and then the difference between the target voltage and the passive voltage change of the distribution network is calculated to serve as the actual distribution network regulation quantity.

9. The power system voltage optimization control method based on digital twin according to claim 1, characterized in that: The process of calculating the regulation amounts of the main grid and distribution network based on regulation priority and coordinated control direction also includes: If the distribution network regulation has a high priority: The maximum deviation of the distribution network voltage is used as the adjustment amount for the distribution network; The product of the distribution network regulation and the voltage transfer coefficient on both sides of the transformer is taken as the passive voltage change of the main grid. Based on the maximum deviation of the main grid voltage, determine the direction in which the main grid itself needs to be adjusted; The difference between the target voltage of the main grid and the current dynamic range boundary of the main grid is calculated, and then the difference between the target voltage and the passive voltage change of the main grid is calculated, which is used as the actual main grid regulation amount.

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