A load capacity evaluation and analysis method and system for power grid regulation

Abstract

This invention discloses a load capacity evaluation and analysis method and system for power grid regulation, specifically relating to the field of quantitative assessment of load carrying capacity in power system dispatching and operation. It addresses the problem that existing static evaluations fail to account for the delay in regulation execution, causing evaluation conclusions to become invalid before the regulation action is completed. This method obtains the current operating status of feeders and the predicted output data of distributed generation sources to determine the predicted operating status at the time the regulation command takes effect. It compares the current and predicted operating states to determine the direction of the feeder's net load offset and whether it is becoming severe. If it is, it determines the dominant driving force. Based on the dominant driving force and the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol, it determines the real-time available regulation capacity of each energy storage system. Using the predicted operating status as a benchmark, it calculates the net load limit at the time the regulation command takes effect and outputs the net load limit to replace the regulation decision-making basis based on the current operating status.

Description

Technical Field

[0001] This invention relates to the field of load capacity quantitative assessment technology in power system dispatching and operation, and more specifically, to a load capacity evaluation and analysis method and system for power grid regulation. Background Technology

[0002] In power system dispatching and operation, to ensure the safe and reliable power supply of the distribution network, it is necessary to conduct a prior assessment of the acceptance capacity of connected distributed photovoltaic, user-side energy storage, and diverse loads. Existing load carrying capacity assessment methods are usually based on power flow calculations, static security constraint verification, or probabilistic statistical analysis at a certain time segment to derive the upper limit of load increments that feeders or distribution areas can accept under the current operating mode. These methods treat the load carrying capacity assessment as a pre-process independent of the control execution process, using a defined cross-sectional state as the assessment input, without taking into account the time delay experienced by the application of the assessment conclusions to the issuance, transmission, and equipment response of control commands.

[0003] Existing technologies suffer from the following problems in scenarios with multiple loads: When the output of distributed power sources fluctuates rapidly due to factors such as changes in weather conditions, there is a non-negligible time lag between the generation of the carrying capacity assessment results and the actual implementation of the control commands. The system operating conditions upon which the static assessment relies have already deviated by the time the actual control is executed, and the validity of the carrying capacity assessment conclusions cannot be maintained until the control action is completed. This leads to the risk of exceeding limits for control operations performed based on the assessment results. This problem directly affects the accuracy and security of distribution network dispatch and control. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a load capacity evaluation and analysis method and system for power grid regulation to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A load capacity evaluation and analysis method for power grid regulation includes the following steps:

[0007] S1: Obtain the current operating status of the feeder and the output prediction data of the distributed power source to determine the predicted operating status of the feeder at the time when the control command takes effect;

[0008] S2: Compare the current operating status with the predicted operating status to determine the direction of feeder net load deviation. When the direction of feeder net load deviation points to the range of increased load rate or voltage over-limit range, the judgment becomes more severe.

[0009] S3: If the situation becomes more severe, compare the changes in power output and load with the current and predicted operating conditions to determine the dominant driving force.

[0010] S4: Based on the dominant driving force, obtain the predicted active power output of each energy storage under the predicted operating state, and combine it with the apparent power constraint in the regulation capability boundary of the energy storage grid connection protocol to determine the real-time available regulation capability of each energy storage.

[0011] S5: Based on the predicted operating status, determine the changes in energy storage output and the corresponding voltage response based on the real-time available adjustment capability, and calculate the net load limit of the feeder at the time when the control command takes effect.

[0012] S6: Output the net load limit as the result of load capacity evaluation, replacing the basis for control decisions based on the current operating status.

[0013] Furthermore, the current operating status of the feeder and the output prediction data of the distributed power source are obtained to determine the predicted operating status of the feeder at the time when the control command takes effect, including:

[0014] Obtain the current operating status of the feeder, which includes the current voltage distribution and current line power flow;

[0015] Obtain distributed power generation output prediction data, which includes the predicted output of distributed photovoltaic power at the time when the control command takes effect;

[0016] By overlaying the distributed power generation output prediction data onto the current operating status, the predicted operating status of the feeder at the time when the control command takes effect is obtained.

[0017] Furthermore, by comparing the current operating status with the predicted operating status, the direction of feeder net load deviation is determined. When the direction of feeder net load deviation points towards the range of increased load rate or voltage exceeding the limit, the situation is considered to be more severe, including:

[0018] Extract the current feeder net load from the current operating status, and extract the predicted feeder net load from the predicted operating status;

[0019] Compare the current net load of the feeder with the predicted net load of the feeder to determine the direction of the net load offset;

[0020] When the direction of the feeder net load shift is such that the predicted feeder net load is greater than the current feeder net load and points to the range of increased load rate, or when the direction of the feeder net load shift points to the range of voltage exceeding the limit, the judgment becomes more severe.

[0021] Furthermore, if the situation worsens, the changes in power output and load under the current and predicted operating conditions are compared to determine the dominant driving force, including:

[0022] Extract the current total power output and current total load power from the current operating status, and extract the predicted total power output and predicted total load power from the predicted operating status;

[0023] The difference between the predicted total power output and the current total power output is calculated as the power output change, and the difference between the predicted total load power and the current total load power is calculated as the load change.

[0024] By comparing the changes in power output with the changes in load, the one with the larger change is identified as the dominant driving force.

[0025] Furthermore, based on the dominant driving force, the predicted active power output of each energy storage unit under predicted operating conditions is obtained. Combined with the apparent power constraint in the regulation capability boundary of the energy storage grid connection protocol, the real-time available regulation capability of each energy storage unit is determined, including:

[0026] Extract the predicted active power output of each energy storage unit from the predicted operating status;

[0027] Extract the apparent power constraints of each energy storage unit from the regulation capacity boundary of the energy storage grid connection protocol;

[0028] Based on the dominant driving force, when the dominant driving force is the change in power output, the real-time available reactive power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints of each energy storage. When the dominant driving force is the change in load, the real-time available active power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints of each energy storage, thus obtaining the real-time available regulation capability of each energy storage.

[0029] Furthermore, the real-time available reactive power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints of each energy storage, including: for each energy storage, subtracting the square of the predicted active power output from the square of the apparent power constraint, and taking the square root of the difference to obtain the real-time available reactive power regulation capability.

[0030] Furthermore, based on the predicted operating status, and considering the real-time available adjustment capability, the changes in energy storage output and the corresponding voltage response are determined. The net load limit of the feeder at the time the control command takes effect is calculated, including:

[0031] The energy storage with the largest real-time adjustable capacity is selected as the dominant energy storage. Based on the predicted operating state, the real-time adjustable capacity of the dominant energy storage is applied to the predicted operating state, and the corresponding voltage response is calculated.

[0032] The voltage response is superimposed on the voltage distribution of the predicted operating state to obtain the regulated voltage distribution;

[0033] Based on the adjusted voltage distribution and feeder safety boundary, the sum of the current load and the allowable load increase of the feeder is taken as the net load limit.

[0034] Furthermore, the real-time available regulation capability of the dominant energy storage is applied to the predicted operating state to calculate the voltage response, including: using the real-time available regulation capability of the dominant energy storage as the reactive power injection, and calculating the voltage change step by step from the grid connection point of the dominant energy storage to each node of the feeder on the voltage distribution of the predicted operating state to obtain the voltage response.

[0035] Furthermore, the output net load limit is used as the load capacity assessment result to replace the control decision-making basis based on the current operating status, including:

[0036] Record the net load limit as the result of the load capacity evaluation.

[0037] The load capacity evaluation results are compared with the control decision-making basis derived from the current operating status;

[0038] Replace the upper limit of the acceptable load increment corresponding to the net load limit in the comparison results with the upper limit of the acceptable load increment derived from the current operating status in the control decision basis, and complete the update of the control decision basis.

[0039] On the other hand, the present invention provides a load capacity evaluation and analysis system for power grid regulation, comprising the following modules:

[0040] The status determination module is used to acquire the current operating status of the feeder and the output prediction data of the distributed power source, and to determine the predicted operating status of the feeder at the time when the control command takes effect.

[0041] The trend determination module is used to compare the current operating status with the predicted operating status to determine the direction of the feeder net load offset. When the feeder net load offset direction points to the load rate increase range or the voltage over-limit range, the determination becomes more severe.

[0042] The drive identification module is used to determine the dominant driving force by comparing the power output change and load change between the current operating state and the predicted operating state when the judgment becomes more severe.

[0043] The capacity determination module is used to obtain the predicted active power output of each energy storage under the predicted operating state based on the dominant driving force, and to determine the real-time available regulation capacity of each energy storage by combining the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol.

[0044] The limit calculation module is used to determine the changes in energy storage output and the corresponding voltage response based on the predicted operating status and the real-time available adjustment capability, and to calculate the net load limit of the feeder at the time when the control command takes effect.

[0045] The results output module is used to output the net load limit as the load capacity evaluation result, replacing the control decision-making basis based on the current operating status.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. By delaying the benchmark time for load capacity evaluation from the current section to the time when the control command takes effect, and comparing the predicted operating status with the current operating status, the direction of feeder net load offset can be identified in advance within the control execution delay. This ensures that the load capacity evaluation and control timing are matched, changing the situation where static evaluation and dynamic control are disconnected. The severity is determined based on whether the offset direction points to the load rate increase range or the voltage over-limit range, avoiding the computational redundancy caused by indiscriminate evaluation of all time periods. At the same time, it identifies the bidirectional risk that voltage over-limit may occur in both the direction of net load increase and decrease, making up for the shortcomings of conventional methods that only focus on changes in one direction. It distinguishes the dominant causes of power output changes and load changes, providing a clear analytical path for subsequent energy storage regulation capacity calculations.

[0048] 2. After determining the dominant driving force, the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol is used, combined with the predicted active power output of the energy storage under the predicted operating conditions, to calculate the real-time available regulation capacity of each energy storage. The actual available margin jointly limited by the apparent power constraint and active power output is used to replace the nominal rated capacity, so that the regulation decision is based on the actual callable capacity of the energy storage. Finally, the real-time available regulation capacity of the dominant energy storage is used to apply the limit, calculate the net load limit at the time when the regulation command takes effect, and directly replace the regulation decision based on the current operating state. The load capacity evaluation result is upgraded from reference information to an executable operation command, reducing the risk of exceeding the limit caused by state deviation during the regulation delay. Attached Figure Description

[0049] Figure 1 This is a flowchart of a load capacity evaluation and analysis method for power grid regulation according to the present invention;

[0050] Figure 2 This is a schematic diagram of the load capacity evaluation and analysis system for power grid regulation according to the present invention. Detailed Implementation

[0051] 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. 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.

[0052] Example 1: Figure 1 This invention presents a load capacity evaluation and analysis method for power grid regulation, which includes the following steps:

[0053] S1: Obtain the current operating status of the feeder and the output prediction data of the distributed power source to determine the predicted operating status of the feeder at the time when the control command takes effect;

[0054] S2: Compare the current operating status with the predicted operating status to determine the direction of feeder net load deviation. When the direction of feeder net load deviation points to the range of increased load rate or voltage over-limit range, the judgment becomes more severe.

[0055] S3: If the situation becomes more severe, compare the changes in power output and load with the current and predicted operating conditions to determine the dominant driving force.

[0056] S4: Based on the dominant driving force, obtain the predicted active power output of each energy storage under the predicted operating state, and combine it with the apparent power constraint in the regulation capability boundary of the energy storage grid connection protocol to determine the real-time available regulation capability of each energy storage.

[0057] S5: Based on the predicted operating status, determine the changes in energy storage output and the corresponding voltage response based on the real-time available adjustment capability, and calculate the net load limit of the feeder at the time when the control command takes effect.

[0058] S6: Output the net load limit as the result of load capacity evaluation, replacing the basis for control decisions based on the current operating status.

[0059] Step S1 involves obtaining the current operating status of the feeder and the output prediction data of the distributed power source, and determining the predicted operating status of the feeder at the time when the control command takes effect. The specific implementation process is as follows.

[0060] The current operating status of the feeder is obtained. The current operating status refers to the real-time electrical quantity information of the feeder collected and recorded by the distribution network dispatch automation system at the evaluation start-up time. This real-time electrical quantity information originates from telemetry data uploaded to the dispatch center by measurement terminals, distribution transformer terminals, or feeder terminal units distributed along the feeder. The current operating status includes the current voltage distribution and the current line power flow. The current voltage distribution refers to the voltage profile data composed of the voltage amplitudes of each node along the feeder. It is obtained by reading the voltage telemetry values ​​of each measurement node of the feeder from the real-time database of the dispatch automation system. For nodes without measurement devices, the voltage estimate is obtained by power flow estimation using the voltage at the feeder head, the load distribution along the line, and the line impedance parameters. The current line power flow refers to the active and reactive power flow status of each branch of the feeder. It is obtained by reading the power telemetry values ​​of each branch of the feeder from the real-time database of the dispatch automation system. For branches without measurement devices, the power flow distribution is calculated by considering the injected power at the nodes and the network topology. The line impedance parameters and network topology used for voltage telemetry, power telemetry, and power flow calculations are all derived from the real-time databases of the distribution network geographic information system and energy management system.

[0061] The project acquires distributed power generation output prediction data, including the predicted output of distributed photovoltaic (PV) power at the time the control command takes effect. The time the control command takes effect refers to the moment when the control action actually takes effect, calculated from the current evaluation start time, including the total delay experienced during the generation, review, issuance, and terminal execution of the control command. The predicted output of distributed PV power at the time the control command takes effect is obtained by using irradiance, temperature, and cloud cover data collected by meteorological monitoring terminals deployed in each distributed PV power station, combined with the PV power station's module tilt angle, conversion efficiency, and historical output characteristics, extrapolated through the irradiance-power conversion relationship.

[0062] The irradiance-power conversion relationship is a mapping curve obtained by fitting multiple sets of measured irradiance values ​​and corresponding measured output power values ​​from historical operating data of photovoltaic power plants. The mapping curve uses irradiance as the input and photovoltaic output power as the output. The mapping curve is divided into monthly sections and fitted separately to reflect the impact of temperature on conversion efficiency under different seasons. The mapping curve is shifted and corrected every fixed period based on the deviation between the recent actual output and the predicted output. The shift correction amount is the difference between the average actual output and the average predicted output over the past week. For distributed photovoltaic systems without meteorological monitoring terminals, the predicted output of distributed photovoltaic systems at the time the control command takes effect is replaced by the spatial interpolation result of the output data of nearby photovoltaic power plants of the same type under similar meteorological conditions. The spatial interpolation method is to select at least three geographically closest photovoltaic power plants of the same type with meteorological monitoring terminals, and use the distance-weighted average of their predicted output as the replacement value.

[0063] The predicted output data of distributed generation sources is superimposed onto the current operating state to obtain the predicted operating state of the feeder at the time the control command takes effect. The superposition method involves determining whether each node in the current voltage distribution of the current operating state is connected to distributed photovoltaic (PV) power. If connected, the predicted output of PV power at the time the control command takes effect is used as the injection power correction for each node, and this is algebraically added to the original injection power of each node in the current operating state. If not connected, the original injection power remains unchanged, thus updating the injection power of each node. For the updated injection power of each node, using the current voltage distribution in the current operating state as the initial voltage distribution and the current line power flow as the initial power flow distribution, a forward-backward power flow calculation is performed using the distribution network topology and line impedance parameters to solve for the updated voltage distribution and line power flow. The solution result is the predicted operating state of the feeder at the time the control command takes effect.

[0064] The forward and backward power flow calculation process involves calculating the active and reactive power distributions of each branch segment by segment from the end node of the feeder to the beginning node. After forward power calculation, the voltage amplitude is calculated node by node from the beginning node to the end node. The voltage amplitude is calculated by subtracting the voltage drop of each branch from the voltage at the beginning node. The voltage drop of each branch is obtained by dividing the product of the branch's transmitted power and its impedance by the node voltage. Forward and backward calculations are performed alternately. After each round of backward calculation, the voltage amplitude calculation result of this round is compared with the voltage amplitude calculation result of the previous round node by node. The iteration terminates when the absolute value of the difference between the two values ​​at all nodes is less than the convergence threshold. The convergence threshold is set according to the accuracy level of the distribution network voltage measurement. The convergence threshold is taken as the lower limit of the error range corresponding to the accuracy class of the distribution network voltage transformer. For example, when the accuracy class of the distribution network voltage transformer is 0.5, the convergence threshold is taken as 0.005 per unit. The predicted operating state of the feeder at the time when the control command takes effect can reflect the system state deviation caused by the change in the output of the distributed power source after the control delay, based on the current operating state. This provides a data basis that conforms to the actual timing of the control for judging the severity of the deviation direction and determining the dominant driving force in subsequent steps.

[0065] Step S1 has obtained the predicted operating status of the feeder at the time when the control command takes effect. Based on this, step S2 is executed to compare the current operating status with the predicted operating status, determine the direction of the feeder net load offset, and determine the severity when the feeder net load offset direction points to the load rate increase range or the voltage over-limit range. The specific implementation process is as follows.

[0066] Extract the current feeder net load from the current operating status. The current feeder net load refers to the difference between the total load power of the feeder and the total output power of distributed generation in the current operating status, reflecting the net power absorbed by the feeder from the upstream power grid. The current feeder net load is extracted by taking the active power value of the current line power flow in the feeder's head branch in the current operating status as the current feeder net load. That is, the active power of the feeder's head branch is read from the current line power flow data in the current operating status. The feeder's head branch refers to the branch between the feeder's outgoing switch and the first branch node.

[0067] The predicted feeder net load is extracted from the predicted operating conditions. The predicted feeder net load refers to the difference between the total load power of the feeder and the total output of distributed generation under the predicted operating conditions, reflecting the predicted net power absorbed by the feeder from the upstream grid after the regulation delay. The predicted feeder net load is extracted by using the active power value of the line power flow at the feeder's head branch under the predicted operating conditions as the predicted feeder net load; that is, the active power of the feeder's head branch is read from the line power flow data under the predicted operating conditions.

[0068] Compare the current feeder net load with the predicted feeder net load to determine the feeder net load offset direction. The feeder net load offset direction refers to the trend of change from the current feeder net load towards the predicted feeder net load. The feeder net load offset direction is determined by the sign of the difference between the predicted and current feeder net loads. The difference between the predicted and current feeder net loads is calculated as: ΔP = Ppred - Pcurr; where ΔP represents the feeder net load difference in kilowatts, Ppred represents the predicted feeder net load in kilowatts, and Pcurr represents the current feeder net load in kilowatts. When ΔP is positive, the feeder net load offset direction is increasing; when ΔP is negative, the feeder net load offset direction is decreasing.

[0069] Determine the specific ranges of the load rate increase range and the voltage over-limit range. The load rate increase range refers to the range where the feeder load rate exceeds the preset load rate threshold and shows an upward trend. The preset load rate threshold is set based on the rated capacity of the distribution transformer connected to the feeder. The preset load rate threshold is taken as the feeder head power value corresponding to 80% of the sum of the rated capacities of the distribution transformers connected to the feeder. When the current load rate of the feeder exceeds the preset load rate threshold and the feeder net load offset direction is increasing, it is determined that the feeder net load offset direction points to the load rate increase range. The voltage over-limit range refers to the range where the lowest voltage along the feeder is lower than the preset lower voltage limit or the highest voltage is higher than the preset upper voltage limit. The preset lower voltage limit is set according to the allowable voltage deviation range of the distribution network. The preset lower voltage limit is 93% of the rated voltage of the feeder, and the preset upper voltage limit is 107% of the rated voltage of the feeder. When there are nodes in the voltage distribution of the predicted operating state where the voltage is lower than the preset lower voltage limit or higher than the preset upper voltage limit, and the direction of the feeder net load offset points to the voltage deterioration trend, it is determined that the direction of the feeder net load offset points to the voltage over-limit range. The voltage deterioration trend refers to the voltage decrease trend corresponding to the direction of increasing feeder net load or the voltage increase trend corresponding to the direction of decreasing feeder net load.

[0070] Severity assessment is performed. A severity assessment is deemed appropriate when the feeder net load shift direction is such that the predicted feeder net load is greater than the current feeder net load and points towards an increasing load rate range. Alternatively, a severity assessment is deemed appropriate when the feeder net load shift direction points towards a voltage over-limit range, regardless of whether the predicted feeder net load is greater than the current feeder net load. For example, if the feeder net load shift direction is increasing, and the voltage at a node in the predicted operating state's voltage distribution is already below the preset lower voltage limit, then a severity assessment is deemed appropriate. Conversely, if the feeder net load shift direction is decreasing, and the voltage at a node in the predicted operating state's voltage distribution is already above the preset upper voltage limit, then a severity assessment is deemed appropriate.

[0071] Step S2 distinguishes between the different sensitivity mechanisms of load rate and voltage dimensions to severity. The load rate increase range focuses only on the single direction of net load increase, while the voltage limit exceedance range identifies the bidirectional risk that can be triggered by both net load increase and decrease, thus avoiding the one-sidedness of existing static evaluations that only focus on whether the limit is exceeded at the current moment without predicting whether the offset direction points to the limit exceedance range. The judgment result of step S2 triggers the dominant driving force determination process in step S3 when the judgment tends to be severe.

[0072] After step S2 determines that the situation is becoming severe, step S3 is executed to compare the changes in power output and load between the current operating state and the predicted operating state to determine the dominant driving force. The specific implementation process is as follows.

[0073] The current total power output and current total load power are extracted from the current operating state. The current total power output refers to the sum of the active power output of all distributed power sources within the feeder range under the current operating state. This is extracted by iterating through the injected power of each node on the feeder in the current operating state, accumulating the injected active power of nodes connected to distributed power sources, with the direction of power injection from the power source to the feeder as the positive value. The current total load power refers to the sum of the active power consumption of all loads within the feeder range under the current operating state. This is extracted by iterating through the load power of each node on the feeder in the current operating state, accumulating the load active power of all nodes, with the direction of power supply from the feeder to the load as the positive value. The node injected power and node load power used for extracting the current total power output and current total load power are derived from the current line power flow data and node voltage data under the current operating state, obtained through decomposition of node power balance relationships.

[0074] The predicted total power output and predicted total load power are extracted from the predicted operating state. The predicted total power output refers to the sum of the active power output of all distributed generation sources within the feeder range under the predicted operating state. This is extracted by iterating through the injected power of each node in the feeder under the predicted operating state and accumulating the injected active power of nodes connected to distributed generation sources. The predicted total load power refers to the sum of the active power consumption of all loads within the feeder range under the predicted operating state. This is extracted by iterating through the load power of each node in the feeder under the predicted operating state and accumulating the load active power of all nodes. The node injected power and node load power used for extracting the predicted total power output and predicted total load power are derived from the line power flow data and voltage distribution data under the predicted operating state. The line power flow data is the updated line power flow obtained after performing the forward-backward substitution power flow calculation in step S1, and the voltage distribution data is the updated voltage distribution obtained in step S1.

[0075] Calculate the changes in power output and load. The change in power output reflects the magnitude of the variation in distributed generation output from the current operating state to the predicted operating state, while the change in load reflects the magnitude of the variation in load power from the current operating state to the predicted operating state. The change in power output is calculated as: ΔPgen = Pgenpred - Pgencurr; where ΔPgen represents the change in power output in kilowatts (kW), Pgenpred represents the predicted total power output in kilowatts (kW), and Pgencurr represents the current total power output in kilowatts (kW). A negative ΔPgen indicates a decrease in distributed generation output, while a positive ΔPgen indicates an increase in distributed generation output.

[0076] The load change is calculated as: ΔPload = Ploadpred - Ploadcurr; where ΔPload represents the load change in kilowatts, Ploadpred represents the predicted total load power in kilowatts, and Ploadcurr represents the current total load power in kilowatts. A positive ΔPload indicates an increase in load power, while a negative ΔPload indicates a decrease in load power.

[0077] Compare the changes in power output and load, and determine the dominant driving force based on the larger change. The comparison method involves taking the absolute value of the power output change and the absolute value of the load change. If the absolute value of the power output change is greater than the absolute value of the load change, the power output change is determined to be the dominant driving force; if the absolute value of the load change is greater than the power output change, the load change is determined to be the dominant driving force. When the absolute values ​​of the power output change and load change are equal, the load change is preferentially determined to be the dominant driving force, based on the fact that the dual degradation effect of load increase on feeder load rate and voltage is more direct than the reduction in power output for the same change magnitude.

[0078] The determination of the dominant driving force identifies the core cause of the severe net load on the feeder. If the dominant driving force is the change in power output, it indicates that the severe situation is mainly driven by fluctuations in distributed power output, and subsequent assessment should focus on the reactive power and voltage support capabilities of energy storage. If the dominant driving force is the change in load, it indicates that the severe situation is mainly driven by changes in load power, and subsequent assessment should focus on the active power regulation capabilities of energy storage. The determination result of the dominant driving force in step S3 will be output to step S4 for selecting the calculation type of the real-time available regulation capability of energy storage.

[0079] Step S3 has determined the dominant driving force. Based on this, step S4 is executed to obtain the predicted active power output of each energy storage under the predicted operating state according to the dominant driving force. Combined with the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol, the real-time available regulation capacity of each energy storage is determined. The specific implementation process is as follows.

[0080] The predicted active power output of each energy storage unit is extracted from the predicted operating state. The predicted active power output of each energy storage unit refers to the active power value of each user-side energy storage unit within the feeder range at the time the control command takes effect under the predicted operating state. A positive value indicates that the energy storage unit absorbs power from the feeder during charging, while a negative value indicates that the energy storage unit injects power into the feeder during discharging. The predicted active power output of each energy storage unit is extracted by reading the injected power data of each grid-connected energy storage node under the predicted operating state. A grid-connected energy storage node refers to the node where each energy storage unit is connected to the feeder through a grid-connected switch. The injected power data comes from the updated injected power of each node obtained when solving the predicted operating state in step S1. For multiple energy storage units connected to the same node, the injected power of the node is allocated according to the rated power ratio registered in the grid connection protocol regulation capacity boundary of each energy storage unit, and the predicted active power output of each energy storage unit is obtained after allocation.

[0081] The apparent power constraints of each energy storage system are extracted from the grid connection protocol's regulation capacity boundary. The grid connection protocol's regulation capacity boundary refers to the adjustable range of the energy storage system explicitly agreed upon in the grid connection agreement signed between the user and the grid dispatching department. This includes the rated active power, rated reactive power, and apparent power constraints of the energy storage system. The apparent power constraint, measured in kilovolt-amperes (kVA), is the maximum allowable apparent power output of the grid-connected inverter and is determined by the inverter's rated capacity. The apparent power constraint value is recorded in the grid connection protocol. The apparent power constraints are extracted by reading the corresponding apparent power constraint field for each energy storage system from the dispatching center's grid connection protocol database. This field is entered during the grid connection acceptance process and periodically verified.

[0082] Based on the dominant driving force determined in step S3, select the type of real-time available regulation capability to calculate for each energy storage unit. When the dominant driving force is the change in power output, the severe situation is mainly caused by fluctuations in distributed power output, and the feeder faces the risk of voltage drop, requiring energy storage to provide reactive power support. In this case, calculate the real-time available reactive power regulation capability for each energy storage unit. When the dominant driving force is the change in load, the severe situation is mainly caused by changes in load power, and the feeder faces the risk of active power overload, requiring energy storage to provide active power support. In this case, calculate the real-time available active power regulation capability for each energy storage unit. The real-time available regulation capability of each energy storage unit is ultimately expressed in the form of active power value or reactive power value, in kilowatts or kilovars.

[0083] When the dominant driving force is the change in power output, the real-time available reactive power regulation capability of each energy storage unit is calculated based on the predicted active power output and apparent power constraints. The calculation method is as follows: for each energy storage unit, subtract the square of the absolute value of the predicted active power output from the square of the apparent power constraint, and take the square root of the difference to obtain the real-time available reactive power regulation capability. The real-time available reactive power regulation capability of each energy storage unit is calculated as: Qavail0 = Slimit 2 -|Ppred| 2The square root of Qavail0 is taken to obtain Qavail, where Qavail0 represents the square of the real-time available reactive power regulation capacity, Qavail represents the real-time available reactive power regulation capacity in kilovars, Slimit represents the apparent power constraint in kilovolt-amperes, and |Ppred| represents the absolute value of the predicted active power output in kilowatts. When |Ppred| is greater than or equal to Slimit, Qavail is zero, indicating that the active power output of the energy storage has fully utilized the inverter capacity, and there is no remaining reactive power regulation capacity.

[0084] When the dominant driving force is load variation, the real-time available active power regulation capacity of each energy storage unit is calculated based on its predicted active power output and apparent power constraints. The real-time available active power regulation capacity of each energy storage unit refers to the upper limit of additional active power that the energy storage unit can provide to the feeder beyond its predicted active power output. The calculation method is to use the apparent power constraint as the upper limit boundary of the energy storage output, and, considering the occupancy of the predicted active power output, use the remaining apparent power margin as the real-time available active power regulation capacity. The real-time available active power regulation capacity of each energy storage unit is calculated as: Pavail = Slimit - |Ppred|; where Pavail represents the real-time available active power regulation capacity in kilowatts, Slimit represents the apparent power constraint in kilovolt-amperes, and |Ppred| represents the absolute value of the predicted active power output in kilowatts. Pavail is zero when |Ppred| is greater than or equal to Slimit.

[0085] The real-time available regulation capacity of each energy storage unit is obtained through the above calculations. When the dominant driving force is the change in power output, the real-time available reactive power regulation capacity of each energy storage unit is output; when the dominant driving force is the change in load, the real-time available active power regulation capacity of each energy storage unit is output. Unlike existing technologies that directly use the rated power in the regulation capacity boundary of the energy storage grid connection protocol as the available regulation capacity, step S4 considers the squeezing effect of the current active power output of the energy storage unit on the reactive or additional active power available margin. By utilizing the apparent power constraint, a protocol parameter ignored by conventional evaluation, the real-time available margin is calculated by predicting the active power output. This allows subsequent load-bearing capacity calculations to be based on the actual available regulation capacity rather than the nominal rated capacity, more accurately reflecting the upper limit of support that the energy storage unit can actually provide under the predicted state at the time the control command takes effect. The real-time available regulation capacity of each energy storage unit output in step S4 will be passed to step S5 to select the dominant energy storage unit and calculate the net load limit of the feeder at the time the control command takes effect.

[0086] Step S4 has output the real-time available regulation capacity of each energy storage unit. Based on this, step S5 is executed. Taking the predicted operating status as a benchmark, the change in energy storage output and the corresponding voltage response are determined based on the real-time available regulation capacity. The net load limit of the feeder at the time when the control command takes effect is calculated. The specific implementation process is as follows.

[0087] The energy storage with the largest real-time available regulation capacity is selected as the dominant energy storage. When the real-time available regulation capacity of each energy storage output in step S4 is the real-time available reactive power regulation capacity of each energy storage, the regulation capacity is compared using the reactive power kilovar value. When the real-time available regulation capacity of each energy storage output in step S4 is the real-time available active power regulation capacity of each energy storage, the regulation capacity is compared using the active power kilowatt value. The real-time available regulation capacity of each energy storage is compared one by one, and the energy storage with the largest value is marked as the dominant energy storage. If multiple energy storages have the same maximum real-time available regulation capacity, the energy storage closest to the feeder head of the grid-connected node is selected as the dominant energy storage. The feeder head refers to the starting point of the branch between the feeder outgoing switch and the first branch node. Closest to the feeder head means that the electrical distance from the grid-connected node to the feeder head along the feeder path is the smallest. The electrical distance is measured by the sum of the impedance moduli of each branch of the feeder.

[0088] Based on the predicted operating state, the entire real-time available regulation capacity of the dominant energy storage is applied to the predicted operating state, and the corresponding voltage response is calculated. When the dominant driving force is the change in power output, the real-time available regulation capacity of the dominant energy storage is the real-time available reactive power regulation capacity. Using the real-time available reactive power regulation capacity of the dominant energy storage as the reactive power injection, the voltage change is calculated step-by-step from the grid connection point of the dominant energy storage to each node of the feeder on the voltage distribution of the predicted operating state, thus obtaining the voltage response. The voltage response refers to the distribution of voltage amplitude changes at each node of the feeder caused by the reactive power injection from the dominant energy storage. The step-by-step calculation process involves taking the grid connection point of the dominant energy storage as the starting node for reactive power injection, with the injected reactive power value equal to the real-time available reactive power regulation capacity of the dominant energy storage, and the direction being from the energy storage to the feeder. The reactive power increment distribution of each branch is calculated segment by segment from the reactive power injection starting node towards the feeder head. The reactive power increment is distributed along the branch according to the impedance ratio. The reactive power increment of each branch is obtained by progressively decreasing the total reactive power injection through the node shunting coefficient, which is the ratio of the equivalent impedance of each branch downstream of the node. After completing the reactive power distribution calculation, the voltage amplitude increment is calculated node by node from the feeder head towards the end. The voltage amplitude increment of each node is obtained by dividing the product of the reactive power increment transmitted by each branch along the path from the feeder head to the corresponding node by the branch reactance, and then dividing by the node voltage reference value. The node voltage reference value is taken as the voltage amplitude of the corresponding node in the predicted operating state. The calculation is repeated node by node until all nodes are covered, and the voltage amplitude increment of each node constitutes the voltage response.

[0089] When the dominant driving force is the load change, the real-time available regulation capability of the dominant energy storage is the real-time available active power regulation capability. Using the real-time available active power regulation capability of the dominant energy storage as the active power injection quantity, and based on the voltage distribution of the predicted operating state, the voltage change is calculated step-by-step from the grid connection point of the dominant energy storage to each node of the feeder to obtain the voltage response. The calculation method for the voltage response under active power injection is as follows: using the real-time available active power regulation capability of the dominant energy storage as the active power injection quantity, the active power increment distribution of each branch is calculated segment by segment from the active power injection starting node towards the feeder head. Then, based on the active power increment distribution and the resistance of each branch, the voltage amplitude increment is calculated node by node from the feeder head to the end. The voltage amplitude increment at each node is obtained by dividing the product of the active power increment transmitted by each branch along the path from the feeder head to the corresponding node by the branch resistance, and then dividing by the node voltage reference value.

[0090] The adjusted voltage distribution is obtained by superimposing the voltage response quantity onto the predicted voltage distribution under operating conditions. The superposition method involves algebraically adding the voltage amplitude of each node in the predicted voltage distribution to the corresponding node's voltage amplitude increment in the voltage response quantity, node by node. A positive voltage amplitude increment indicates a voltage increase, while a negative increment indicates a voltage decrease. The summation yields the adjusted voltage distribution. The adjusted voltage distribution reflects the expected voltage state of each node in the feeder after the dominant energy storage system supports the entire real-time adjustable capacity.

[0091] Based on the adjusted voltage distribution and feeder safety boundaries, the sum of the current load and the allowable load increase is taken as the net load limit. The feeder safety boundaries include a preset upper voltage limit, a preset lower voltage limit, and a line thermal stability boundary. The preset upper voltage limit is 107% of the feeder's rated voltage, and the preset lower voltage limit is 93% of the feeder's rated voltage. The line thermal stability boundary refers to the maximum apparent power that each branch of the feeder is allowed to continuously transmit. It is determined by the feeder conductor type and laying method. The line thermal stability boundary is obtained by reading the allowable current carrying capacity of each branch from the feeder equipment ledger and converting it into an allowable apparent power value. The allowable load increase refers to the maximum load increment when the adjusted voltage distribution simultaneously meets the following conditions: the voltage at each node in the adjusted voltage distribution is not lower than the preset lower voltage limit and not higher than the preset upper voltage limit, and the apparent power of each branch in the adjusted line power flow does not exceed the line thermal stability boundary. The method for determining the load that can be increased is to start from the current load of the feeder and gradually increase the total load power of the feeder in fixed steps. The fixed step size is set according to the minimum single capacity of the distribution transformer connected to the feeder. After each increase, the voltage distribution and line power flow of the feeder are recalculated according to the forward-backward substitution power flow calculation method in step S1, until any node or branch in the voltage distribution and line power flow touches the safety boundary of the feeder. The load increment one step before touching the boundary is the load that can be increased. The net load limit is obtained by adding the current load of the feeder to the load that can be increased.

[0092] Step S5 simulates the system state after the energy storage provides maximum support at the moment the control command takes effect by selecting the dominant energy storage and applying its actual available regulation capacity to the limit, rather than relying on general assumptions based on rated parameters or historical data. The calculated net load limit directly corresponds to the upper limit of the load increment that the feeder can withstand at the moment the control command takes effect, making the load capacity evaluation results output in the subsequent step S6 have clear guidance significance for control operations.

[0093] Step S5 has calculated the net load limit of the feeder at the time when the control command takes effect. Based on this, step S6 is executed to output the net load limit as the load capacity evaluation result, replacing the control decision based on the current operating status. The specific implementation process is as follows.

[0094] The net load limit is recorded as the load capacity evaluation result. The net load limit is the upper limit of the load increment that the feeder can withstand at the time the control command takes effect, calculated in step S5. It is measured in kilowatts and represents the maximum net load power allowed within the feeder's safety boundary after the dominant energy storage provides support with all its real-time available regulation capacity. The load capacity evaluation result refers to the final evaluation conclusion given by the dispatch center on the feeder's load capacity to accept during the current dispatch cycle. The load capacity evaluation result includes the net load limit value, the dominant driving force, the dominant energy storage identifier, and the evaluation generation time. The load capacity evaluation result is recorded by creating a new evaluation record in the evaluation result database of the dispatch automation system. The net load limit value is written into the upper limit of the acceptable load increment field of the evaluation record, the dominant driving force determined in step S3 is written into the dominant driving force field of the evaluation record, the identifier of the dominant energy storage selected in step S5 is written into the dominant energy storage field of the evaluation record, and the current system clock time is written into the evaluation generation time field of the evaluation record. The evaluation record is stored in association with the feeder identifier.

[0095] The load capacity assessment results are compared with the control decision criteria derived from the current operating state. The control decision criteria derived from the current operating state refer to the upper limit of the acceptable load increment obtained after calculating the carrying capacity of the current operating state using the static section assessment method. The static section assessment method does not consider the system state deviation at the time the control command takes effect. The control decision criteria derived from the current operating state are stored in the real-time decision database of the dispatch automation system. The comparison method involves retrieving the upper limit of the acceptable load increment recorded in the control decision criteria derived from the current operating state corresponding to the feeder identifier from the real-time decision database of the dispatch automation system, and then comparing the net load limit value in the load capacity assessment results with the upper limit of the acceptable load increment recorded in the control decision criteria derived from the current operating state.

[0096] The upper limit of the acceptable load increment corresponding to the net load limit in the comparison results will replace the upper limit of the acceptable load increment derived from the current operating status in the control decision basis, thus completing the update of the control decision basis. The replacement method involves updating the original value of the upper limit of the acceptable load increment field in the control decision basis record corresponding to the feeder identifier in the real-time decision database of the dispatch automation system to the net load limit value in the load capacity evaluation results. Simultaneously, the evaluation generation time will be written into the update time field of the control decision basis record, while other fields in the control decision basis record will remain unchanged. After the update, the dispatch center will use the updated control decision basis as the execution standard in subsequent control operations such as load access approval, power generation plan adjustment, and safety verification, replacing the original control decision basis derived from the current operating status.

[0097] Step S6 completes the entire process of load capacity evaluation and analysis. By formally outputting the net load limit calculated based on the predicted state and the actual available regulation capacity and replacing the static evaluation results, the control decision is based on the prediction of the system state at the time the control command takes effect, thus eliminating the problem of the control decision basis becoming invalid due to the state deviation within the evaluation-execution time window.

[0098] Example 2: Figure 2 A schematic diagram of a load capacity evaluation and analysis system for power grid regulation is provided according to the present invention. The load capacity evaluation and analysis system for power grid regulation includes the following modules:

[0099] The status determination module is used to acquire the current operating status of the feeder and the output prediction data of the distributed power source, and to determine the predicted operating status of the feeder at the time when the control command takes effect.

[0100] The trend determination module is used to compare the current operating status with the predicted operating status to determine the direction of the feeder net load offset. When the feeder net load offset direction points to the load rate increase range or the voltage over-limit range, the determination becomes more severe.

[0101] The drive identification module is used to determine the dominant driving force by comparing the power output change and load change between the current operating state and the predicted operating state when the judgment becomes more severe.

[0102] The capacity determination module is used to obtain the predicted active power output of each energy storage under the predicted operating state based on the dominant driving force, and to determine the real-time available regulation capacity of each energy storage by combining the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol.

[0103] The limit calculation module is used to determine the changes in energy storage output and the corresponding voltage response based on the predicted operating status and the real-time available adjustment capability, and to calculate the net load limit of the feeder at the time when the control command takes effect.

[0104] The results output module is used to output the net load limit as the load capacity evaluation result, replacing the control decision-making basis based on the current operating status.

[0105] All calculations involved in the embodiments are dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.

[0106] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0107] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

Claims

1. A load capacity evaluation and analysis method for power grid regulation, characterized in that, Includes the following steps: S1: Obtain the current operating status of the feeder and the output prediction data of the distributed power source to determine the predicted operating status of the feeder at the time when the control command takes effect; S2: Compare the current operating status with the predicted operating status to determine the direction of feeder net load deviation. When the direction of feeder net load deviation points to the range of increased load rate or voltage over-limit range, the judgment becomes more severe. S3: If the situation becomes more severe, compare the changes in power output and load with the current and predicted operating conditions to determine the dominant driving force. S4: Based on the dominant driving force, obtain the predicted active power output of each energy storage under the predicted operating state, and combine it with the apparent power constraint in the regulation capability boundary of the energy storage grid connection protocol to determine the real-time available regulation capability of each energy storage. S5: Based on the predicted operating status, determine the changes in energy storage output and the corresponding voltage response based on the real-time available adjustment capability, and calculate the net load limit of the feeder at the time when the control command takes effect. S6: Output the net load limit as the result of load capacity evaluation, replacing the basis for control decisions based on the current operating status.

2. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, Obtain the current operating status of the feeder and the predicted output data of the distributed power source to determine the predicted operating status of the feeder at the time when the control command takes effect, including: Obtain the current operating status of the feeder, which includes the current voltage distribution and current line power flow; Obtain distributed power generation output prediction data, which includes the predicted output of distributed photovoltaic power at the time when the control command takes effect; By overlaying the distributed power generation output prediction data onto the current operating status, the predicted operating status of the feeder at the time when the control command takes effect is obtained.

3. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, By comparing the current operating status with the predicted operating status, the direction of feeder net load deviation is determined. When the feeder net load deviation direction points towards the range of increased load rate or voltage exceeding the limit, the situation is considered to be more severe, including: Extract the current feeder net load from the current operating status, and extract the predicted feeder net load from the predicted operating status; Compare the current net load of the feeder with the predicted net load of the feeder to determine the direction of the net load offset; When the direction of the feeder net load shift is such that the predicted feeder net load is greater than the current feeder net load and points to the range of increased load rate, or when the direction of the feeder net load shift points to the range of voltage exceeding the limit, the judgment becomes more severe.

4. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, If the situation worsens, compare the changes in power output and load under the current and predicted operating conditions to determine the dominant driving force, including: Extract the current total power output and current total load power from the current operating status, and extract the predicted total power output and predicted total load power from the predicted operating status; The difference between the predicted total power output and the current total power output is calculated as the power output change, and the difference between the predicted total load power and the current total load power is calculated as the load change. By comparing the changes in power output with the changes in load, the one with the larger change is identified as the dominant driving force.

5. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, Based on the dominant driving force, the predicted active power output of each energy storage unit under predicted operating conditions is obtained. Combined with the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol, the real-time available regulation capacity of each energy storage unit is determined, including: Extract the predicted active power output of each energy storage unit from the predicted operating status; Extract the apparent power constraints of each energy storage unit from the regulation capacity boundary of the energy storage grid connection protocol; Based on the dominant driving force, when the dominant driving force is the change in power output, the real-time available reactive power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints of each energy storage. When the dominant driving force is the change in load, the real-time available active power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints of each energy storage, thus obtaining the real-time available regulation capability of each energy storage.

6. The load capacity evaluation and analysis method for power grid regulation according to claim 5, characterized in that, The real-time available reactive power regulation capability of each energy storage is calculated based on the predicted active power output and apparent power constraints. This includes: for each energy storage, subtracting the square of the predicted active power output from the square of the apparent power constraint, and taking the square root of the difference to obtain the real-time available reactive power regulation capability.

7. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, Based on the predicted operating status, the changes in energy storage output and the corresponding voltage response are determined according to the real-time available adjustment capability. The net load limit of the feeder at the time the control command takes effect is calculated, including: The energy storage with the largest real-time adjustable capacity is selected as the dominant energy storage. Based on the predicted operating state, the real-time adjustable capacity of the dominant energy storage is applied to the predicted operating state, and the corresponding voltage response is calculated. The voltage response is superimposed on the voltage distribution of the predicted operating state to obtain the regulated voltage distribution; Based on the adjusted voltage distribution and feeder safety boundary, the sum of the current load and the allowable load increase of the feeder is taken as the net load limit.

8. The load capacity evaluation and analysis method for power grid regulation according to claim 7, characterized in that, The real-time available regulation capacity of the dominant energy storage is applied to the predicted operating state to calculate the voltage response, including: using the real-time available regulation capacity of the dominant energy storage as the reactive power injection, and calculating the voltage change step by step from the grid connection point of the dominant energy storage to each node of the feeder on the voltage distribution of the predicted operating state to obtain the voltage response.

9. The load capacity evaluation and analysis method for power grid regulation according to claim 1, characterized in that, Outputting the net load limit as the result of load capacity evaluation, replacing the basis for control decisions based on the current operating status, including: Record the net load limit as the result of the load capacity evaluation. The load capacity evaluation results are compared with the control decision-making basis derived from the current operating status; Replace the upper limit of the acceptable load increment corresponding to the net load limit in the comparison results with the upper limit of the acceptable load increment derived from the current operating status in the control decision basis, and complete the update of the control decision basis.

10. A load capacity evaluation and analysis system for power grid regulation, used to implement the load capacity evaluation and analysis method for power grid regulation as described in any one of claims 1-9, characterized in that, Includes the following modules: The status determination module is used to acquire the current operating status of the feeder and the output prediction data of the distributed power source, and to determine the predicted operating status of the feeder at the time when the control command takes effect. The trend determination module is used to compare the current operating status with the predicted operating status to determine the direction of the feeder net load offset. When the feeder net load offset direction points to the load rate increase range or the voltage over-limit range, the determination becomes more severe. The drive identification module is used to determine the dominant driving force by comparing the power output change and load change between the current operating state and the predicted operating state when the judgment becomes more severe. The capacity determination module is used to obtain the predicted active power output of each energy storage under the predicted operating state based on the dominant driving force, and to determine the real-time available regulation capacity of each energy storage by combining the apparent power constraint in the regulation capacity boundary of the energy storage grid connection protocol. The limit calculation module is used to determine the changes in energy storage output and the corresponding voltage response based on the predicted operating status and the real-time available adjustment capability, and to calculate the net load limit of the feeder at the time when the control command takes effect. The results output module is used to output the net load limit as the load capacity evaluation result, replacing the control decision-making basis based on the current operating status.

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