Voltage-power relationship modeling method and system for grid-connected point of distribution network

Abstract

The application provides a power distribution network grid-connected point voltage-power relationship modeling method and system, calculates equivalent access impedance between each grid-connected point and a superior power grid according to a power distribution network topological structure, line parameters and transformer parameters, and constructs an access impedance difference model; a voltage-power relationship model between a grid-connected point voltage and active power and reactive power is established on the basis of considering the access impedance difference, real-time operation data is input into the model to correct and update model parameters, and accurate modeling of a grid-connected point voltage-power change relationship is realized. The application can effectively depict voltage response characteristic differences of different grid-connected points caused by access impedance differences, improve grid-connected point voltage prediction accuracy and regulation reliability, and provides technical support for distributed power grid connection, voltage regulation and reverse power management.

Description

Technical Field

[0001] This invention relates to the field of power system technology, specifically to a method and system for modeling the voltage-power relationship at the grid connection point of a distribution network. More particularly, it relates to a method and system for modeling the voltage-power relationship at the grid connection point of a distribution network that considers differences in access impedance. Background Technology

[0002] With the large-scale integration of distributed photovoltaic (PV) and wind power generation into the distribution network, the distribution network has gradually evolved from a traditional unidirectional power supply structure to a new bidirectional power flow operation mode, significantly increasing its operational complexity and uncertainty. Especially during periods of high PV power output and low local load, reverse power flow (power being fed back into the upstream grid) can easily occur, leading to problems such as grid connection voltage rise, voltage exceeding limits, and three-phase imbalance, severely impacting the safety and power quality of the distribution network. Therefore, accurately characterizing the relationship between grid connection voltage and active and reactive power is crucial for achieving grid-friendly integration of distributed power sources and refined voltage control of the distribution network.

[0003] Currently, most voltage-power relationship models widely used in distribution networks are based on the assumption of uniform equivalent impedance or three-phase balance, treating the lines and transformers between different users and different access points to the grid as having the same impedance parameters. Although these models are simple in form and easy to analyze and control, they are difficult to reflect the inconsistencies in access impedance caused by differences in feeder length, conductor specifications, access location, and load distribution in actual distribution networks. As a result, they often produce large voltage prediction errors in scenarios with a high proportion of distributed power sources, making it difficult to meet the needs of refined regulation and safety assessment.

[0004] Although existing research has proposed grid-connected point voltage analysis methods based on power flow calculations or equivalent models, these methods typically ignore or weaken the impact of differences in connection impedance at different grid-connected points on the voltage-power relationship, making it difficult to accurately describe the true response characteristics of each grid-connected point and each phase voltage under reverse power conditions. Since differences in connection impedance directly determine the sensitivity of voltage to changes in active and reactive power, failure to reflect this in the model will lead to inaccurate control strategy design, and may even cause problems such as excessive power limiting or control failure. Therefore, constructing a modeling method for distribution network grid-connected point voltage-power relationship that can consider differences in connection impedance is of great significance for improving voltage prediction accuracy and control reliability.

[0005] Patent application CN115800370A discloses a method for optimizing the configuration of distributed power sources in a distribution network and a computer-readable medium to reduce energy consumption and improve voltage quality in distribution networks containing distributed power sources. First, a distribution network model containing multiple distributed power sources is initialized. Second, a multi-objective optimization model of the distribution network is constructed with the goals of minimizing active power loss, minimizing voltage deviation, and maximizing voltage stability, and corresponding equality and inequality constraints are designed. Then, an improved transient search optimization algorithm is used to solve the multi-objective optimization model of the distribution network, employing a global search and local optimization process by setting adjustment coefficients and step size coefficients to balance the algorithm. Finally, the globally optimal solution is obtained, achieving the optimized configuration of distributed power sources in the distribution network model. However, this patent application cannot completely solve the existing technical problems and does not meet the needs of this invention. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for modeling the voltage-power relationship at the grid connection point of a power distribution network.

[0007] The voltage-power relationship modeling method for distribution network connection points provided by the present invention includes:

[0008] Step 1: Obtain the distribution network topology, line parameters, and transformer parameters, and collect voltage, active power, and reactive power operation data at each grid connection point; Step 2: Based on the distribution network topology and line parameters, calculate the equivalent access impedance between each grid connection point and the upper-level power grid to obtain the access impedance parameters that reflect the differences in electrical distance between different grid connection points; Step 3: Construct an access impedance difference model based on the access impedance parameters, and group or identify each grid connection point according to its access impedance characteristics; Step 4: Based on the aforementioned access impedance difference model, establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power to obtain the grid connection point PQV model containing access impedance difference information. Step 5: Input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the grid connection point voltage-power relationship that reflects the current operating status; Step 6: Using the updated grid connection point voltage-power relationship model, predict or perform sensitivity analysis on the grid connection point voltage, and output the response results of each grid connection point voltage to changes in active and reactive power.

[0009] Preferably, step 2 includes: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance. :

[0010] in, , Equivalent resistance , For equivalent reactance, Let k be the set of lines and transformers between the grid connection point and the upstream power grid. The index, j, is the imaginary unit; this access impedance is used to characterize the electrical distance of the grid connection point in the distribution network and its impact on voltage changes.

[0011] Preferably, step 3 includes: An impedance weighting factor is introduced to characterize the proportional relationship between the active and reactive power effects on voltage:

[0012] in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes. The equivalent access impedance of each grid connection point is used as the input parameter. The grid connection points are classified according to the impedance weighting factor. Grid connection points with similar access impedance characteristics within the preset range are grouped into the same group, and grid connection points with similar access impedance characteristics outside the preset range are divided into different groups. At the same time, the grid connection points in different groups are marked for model parameter correction and location in actual application.

[0013] Preferably, step 4 includes: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now:

[0014] in, The equivalent voltage source voltage of the upstream power grid at the grid connection point; For grid connection point The active power; For grid connection point reactive power; The voltage at grid connection point i The conjugate of complex numbers; Furthermore, its nonlinear PQV relationship is obtained:

[0015] Take under normal operation Linearizing the above relationship to the first order, we get:

[0016] in, , , These are the grid connection point voltage, active power, and reactive power changes, respectively. Define voltage sensitivity:

[0017] This sensitivity parameter characterizes the voltage change caused by a unit change in active power or a unit change in reactive power. A larger sensitivity value indicates a more significant impact of the corresponding power change on the voltage. Simultaneously, to account for the influence of nonlinear factors, a second-order sensitivity is defined.

[0018] When the photovoltaic output exceeds the load, that is ,but:

[0019] Reverse power causes a voltage rise, and its over-limit condition is:

[0020] in, This is the maximum allowable operating voltage at the grid connection point; This leads to the critical value for inverse power:

[0021] in, For grid connection point The maximum reverse power allowed without voltage over-limit; when photovoltaic output reaches this critical value, power limiting measures are taken to avoid voltage over-limit; impedance grouping. Calculate the equivalent parameters of this group; the equivalent parameters are:

[0022] in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined; based on these equivalent parameters, a PQV model at the group level is established:

[0023] in, , , Impedance grouping The changes in grid connection point voltage, active power, and reactive power.

[0024] Preferably, step 5 includes: The equivalent access impedance parameters are dynamically corrected by minimizing the error function, so that the model reflects the current operating state of the distribution network.

[0025] in, For a moment At the grid connection point The actual voltage value measured at the location; Step 6 includes: With power regulation amount At that time, the predicted voltage at the grid connection point is:

[0026] in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value; To meet voltage constraints The required active power regulation is:

[0027] The calculation results are directly applied to the operation and control of the distribution network. When the predicted voltage will exceed the upper limit, the distributed power generation is limited based on the calculated active power regulation, or the excess active power is absorbed by energy storage devices. At the same time, combined with reactive power regulation optimization, reactive power output is adjusted by reactive power compensation devices to ensure that the voltage remains stable within the allowable range.

[0028] The voltage-power relationship modeling system for distribution network connection points provided by the present invention includes a data acquisition module, an access impedance calculation module, an impedance difference modeling module, a PQV model construction module, a parameter correction module, and a voltage prediction and control decision module. The data acquisition module is used to obtain the distribution network topology, line parameters and transformer parameters, and to collect voltage, active power and reactive power operation data of each grid connection point; The access impedance calculation module is used to calculate the equivalent access impedance between each grid connection point and the upper-level power grid based on the distribution network topology and line parameters, so as to obtain access impedance parameters that reflect the differences in electrical distance between different grid connection points. The impedance difference modeling module is used to construct an access impedance difference model based on the access impedance parameters, and to group or identify each grid connection point according to the access impedance characteristics. The PQV model construction module is used to establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power based on the access impedance difference model, so as to obtain a grid connection point PQV model containing access impedance difference information. The parameter correction module is used to input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the grid connection point voltage-power relationship that reflects the current operating status. The voltage prediction and control decision module is used to predict or perform sensitivity analysis on the grid connection point voltage using the updated grid connection point voltage-power relationship model, and output the response results of each grid connection point voltage to changes in active and reactive power.

[0029] Preferably, the access impedance calculation module includes: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance. :

[0030] in, , Equivalent resistance , For equivalent reactance, Let k be the set of lines and transformers between the grid connection point and the upstream power grid. The index, j, is the imaginary unit; this access impedance is used to characterize the electrical distance of the grid connection point in the distribution network and its impact on voltage changes.

[0031] Preferably, the impedance difference modeling module includes: An impedance weighting factor is introduced to characterize the proportional relationship between the active and reactive power effects on voltage:

[0032] in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes. The equivalent access impedance of each grid connection point is used as the input parameter. The grid connection points are classified according to the impedance weighting factor. Grid connection points with similar access impedance characteristics within the preset range are grouped into the same group, and grid connection points with similar access impedance characteristics outside the preset range are divided into different groups. At the same time, the grid connection points in different groups are marked for model parameter correction and location in actual application.

[0033] Preferably, the PQV model building module includes: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now:

[0034] in, The equivalent voltage source voltage of the upstream power grid at the grid connection point; For grid connection point The active power; For grid connection point reactive power; The voltage at grid connection point i The conjugate of complex numbers; Furthermore, its nonlinear PQV relationship is obtained:

[0035] Take under normal operation Linearizing the above relationship to the first order, we get:

[0036] in, , , These are the grid connection point voltage, active power, and reactive power changes, respectively. Define voltage sensitivity:

[0037] This sensitivity parameter characterizes the voltage change caused by a unit change in active power or a unit change in reactive power. A larger sensitivity value indicates a more significant impact of the corresponding power change on the voltage. Simultaneously, to account for the influence of nonlinear factors, a second-order sensitivity is defined.

[0038] When the photovoltaic output exceeds the load, that is ,but:

[0039] Reverse power causes a voltage rise, and its over-limit condition is:

[0040] in, This is the maximum allowable operating voltage at the grid connection point; This leads to the critical value for inverse power:

[0041] in, For grid connection point The maximum reverse power allowed without voltage over-limit; when photovoltaic output reaches this critical value, power limiting measures are taken to avoid voltage over-limit; impedance grouping. Calculate the equivalent parameters of this group; the equivalent parameters are:

[0042] in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined; based on these equivalent parameters, a PQV model at the group level is established:

[0043] in, , , Impedance grouping The changes in grid connection point voltage, active power, and reactive power.

[0044] Preferably, the parameter correction module includes: The equivalent access impedance parameters are dynamically corrected by minimizing the error function, so that the model reflects the current operating state of the distribution network.

[0045] in, For a moment At the grid connection point The actual voltage value measured at the location; The voltage prediction and control decision module includes: With power regulation amount At that time, the predicted voltage at the grid connection point is:

[0046] in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value; To meet voltage constraints The required active power regulation is:

[0047] The calculation results are directly applied to the operation and control of the distribution network. When the predicted voltage will exceed the upper limit, the distributed power generation is limited based on the calculated active power regulation, or the excess active power is absorbed by energy storage devices. At the same time, combined with reactive power regulation optimization, reactive power output is adjusted by reactive power compensation devices to ensure that the voltage remains stable within the allowable range.

[0048] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for modeling the voltage-power relationship at grid connection points in a distribution network, considering differences in access impedance. First, the method calculates the equivalent access impedance of different grid connection points using the distribution network topology and line parameters, and then depicts the differences in electrical distance and impedance characteristics at each connection point. Second, based on the traditional voltage-power relationship model, an access impedance difference parameter is introduced, enabling the model to reflect the differences in the degree of impact of active and reactive power changes on voltage at different grid connection points. Furthermore, the model parameters are corrected and updated using real-time measurement data, allowing the established PQV model to adapt to changes in the operating state of the distribution network. In practical applications, this method can more accurately predict the voltage change trend and sensitivity at grid connection points, providing a reliable basis for voltage regulation, reverse power management, and refined operation of distribution networks, such as photovoltaic and other distributed power sources, thereby improving the safety, stability, and operating efficiency of the distribution network. Attached Figure Description

[0049] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart of the distribution network connection point voltage-power relationship modeling method considering the difference in access impedance in this invention; Figure 2 This is a schematic diagram illustrating the access impedance difference modeling and partitioning of the present invention; Figure 3 This is a schematic diagram of the grid connection point voltage-power relationship modeling structure of the present invention. Detailed Implementation

[0050] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0051] Example like Figure 1 As shown, this invention provides a method for modeling the voltage-power relationship at the grid connection point of a distribution network that considers differences in access impedance, comprising the following steps: Obtain the distribution network topology, line parameters, and transformer parameters, and collect voltage, active power, and reactive power operation data at each grid connection point; Based on the distribution network topology and line parameters, the equivalent access impedance between each grid connection point and the upper-level power grid is calculated to obtain the access impedance parameters that reflect the differences in electrical distance between different grid connection points. Based on the access impedance parameters, an access impedance difference model is constructed, and each grid connection point is grouped or identified according to its access impedance characteristics. Based on the aforementioned access impedance difference model, a voltage-power relationship model between the voltage of each grid connection point and active and reactive power is established to obtain a grid connection point PQV model that includes access impedance difference information. The real-time collected grid connection point voltage and power data are input into the PQV model to correct and update the model parameters, thereby obtaining the grid connection point voltage-power relationship that reflects the current operating status. Using the updated grid connection point voltage-power relationship model, the grid connection point voltage is predicted or its sensitivity is analyzed, and the response results of each grid connection point voltage to changes in active and reactive power are output.

[0052] The specific method for obtaining the distribution network topology, line parameters, and transformer parameters, and collecting voltage, active power, and reactive power operation data at each grid connection point is as follows: Acquire distribution network operation data, including distribution network topology, line resistance, line reactance, transformer parameters, and voltage amplitude, active power, and reactive power of each grid connection point; model each grid connection point and line as network nodes and branches according to the distribution network topology, and form an equivalent model of the distribution network to describe the electrical connection relationship between each grid connection point and the upper-level power grid.

[0053] The specific method for calculating the equivalent connection impedance of each grid connection point based on the distribution network topology and line parameters is as follows: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance:

[0054] in, Equivalent resistance For equivalent reactance, This refers to the collection of lines and transformers between the grid connection point and the upstream power grid. The connection impedance characterizes the electrical distance of the grid connection point within the distribution network and its impact on voltage variations.

[0055] like Figure 2 As shown, the specific method for constructing the access impedance difference model and grouping or identifying each grid connection point is as follows: Because the equivalent connection impedance differs at different grid connection points, the proportions of active and reactive power's influence on the voltage at each point vary. To accurately characterize this difference and facilitate subsequent targeted modeling, a model of connection impedance difference is constructed, and the grid connection points are grouped or labeled. To characterize the connection impedance difference, an impedance weighting factor is introduced to represent the proportional relationship between the active and reactive power's influence on voltage.

[0056] in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes.

[0057] Using the equivalent connection impedance of each grid connection point as the input parameter, the grid connection points are classified according to the impedance weighting factor. Grid connection points with similar impedance weighting factors (i.e., similar connection impedance characteristics) are grouped together, while those with significantly different impedance weighting factors (i.e., significantly different connection impedance characteristics) are grouped into different groups. This grouping method ensures that grid connection points within the same group exhibit similar voltage-power response characteristics, creating conditions for simplified modeling and improved model accuracy. Simultaneously, clearly identifying grid connection points in different groups facilitates rapid location during subsequent model parameter calibration and practical applications.

[0058] The specific method for establishing the PQV model of the grid connection point based on the impedance difference model is as follows: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now:

[0059] in, This is the equivalent voltage source voltage of the upstream power grid at the grid connection point. Further, its nonlinear PQV relationship can be obtained:

[0060] Take under normal operation Linearizing the above relationship to the first order, we get:

[0061] in, , , These represent the changes in grid connection point voltage, active power, and reactive power, respectively.

[0062] Define voltage sensitivity:

[0063] This sensitivity parameter characterizes the voltage change caused by a unit change in active power or a unit change in reactive power. A higher sensitivity value indicates a more significant impact of the corresponding power change on the voltage. Furthermore, to account for the influence of nonlinear factors, a second-order sensitivity is also defined:

[0064] When the photovoltaic output exceeds the load, that is ,but:

[0065] Reverse power causes a voltage rise, and its over-limit condition is:

[0066] in, This is the maximum allowable operating voltage at the grid connection point. From this, the inverse power critical value is obtained:

[0067] in, For grid connection point The maximum permissible reverse power without voltage overshoot. This critical value provides an important basis for the output control of distributed generation. When photovoltaic output reaches this critical value, measures such as power limiting must be taken to avoid voltage overshoot. Impedance grouping. The equivalent parameters for this group need to be calculated. The equivalent parameters are:

[0068] in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined. Based on these equivalent parameters, a group-level PQV model can be established:

[0069] The specific method for inputting real-time collected grid connection point voltage and power data into the PQV model and correcting and updating the model parameters is as follows: By minimizing the error function:

[0070] in, For a moment At the grid connection point The actual voltage value measured at the location. The equivalent access impedance parameters are dynamically corrected to ensure that the model reflects the current operating state of the distribution network.

[0071] The specific method for predicting voltage or performing sensitivity analysis using the updated grid connection point voltage-power relationship model is as follows: With power regulation amount At that time, the predicted voltage at the grid connection point is:

[0072] in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value. This predicted value can inform operators in advance of the voltage change trend after power adjustment, providing a basis for whether to implement the adjustment plan. To meet voltage constraints. The required active power regulation is:

[0073] The calculation results can be directly applied to the operation and control of the distribution network. When the predicted voltage will exceed the upper limit, the power generation of distributed power sources such as photovoltaics can be limited based on the calculated active power regulation, or the excess active power can be absorbed by energy storage devices. At the same time, combined with the optimization of reactive power regulation, the reactive power output can be adjusted by reactive power compensation devices to ensure that the voltage remains stable within the allowable range.

[0074] like Figure 3 As shown, the present invention provides a voltage-power relationship modeling system for distribution network connection points that considers the difference in access impedance, including: a data acquisition module, an access impedance calculation module, an impedance difference modeling module, a PQV model construction module, a parameter correction module, and a voltage prediction and control decision module; The data acquisition module is used to obtain the distribution network topology, line parameters and transformer parameters, and to collect voltage, active power and reactive power operation data of each grid connection point; The access impedance calculation module is used to calculate the equivalent access impedance between each grid connection point and the upper-level power grid based on the distribution network topology and line parameters, so as to obtain access impedance parameters that reflect the differences in electrical distance between different grid connection points. The impedance difference modeling module is used to construct an access impedance difference model based on the access impedance parameters, and to group or identify each grid connection point according to the access impedance characteristics. The PQV model construction module is used to establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power based on the access impedance difference model, so as to obtain a grid connection point PQV model containing access impedance difference information. The parameter correction module is used to input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the grid connection point voltage-power relationship that reflects the current operating status. The voltage prediction and control decision module is used to predict or perform sensitivity analysis on the grid connection point voltage using the updated grid connection point voltage-power relationship model, and output the response results of each grid connection point voltage to changes in active and reactive power.

[0075] The data acquisition module is used to obtain the distribution network topology, line parameters, and transformer parameters, and the specific method for collecting voltage, active power, and reactive power operating data at each grid connection point is as follows: Acquire distribution network operation data, including distribution network topology, line resistance, line reactance, transformer parameters, and voltage amplitude, active power, and reactive power of each grid connection point; model each grid connection point and line as network nodes and branches according to the distribution network topology, and form an equivalent model of the distribution network to describe the electrical connection relationship between each grid connection point and the upper-level power grid.

[0076] The access impedance calculation module is used to calculate the equivalent access impedance between each grid connection point and the upper-level grid based on the distribution network topology and line parameters. The specific method for obtaining the access impedance parameters reflecting the differences in electrical distance between different grid connection points is as follows: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance:

[0077] in, Equivalent resistance For equivalent reactance, This refers to the collection of lines and transformers between the grid connection point and the upstream power grid. The connection impedance characterizes the electrical distance of the grid connection point within the distribution network and its impact on voltage variations.

[0078] The impedance difference modeling module is used to construct an access impedance difference model based on the access impedance parameters, and the specific method for grouping or identifying each grid connection point according to the access impedance characteristics is as follows: To characterize the difference in connection impedance, an impedance weighting factor is introduced to represent the proportional relationship between the effects of active and reactive power on voltage.

[0079] in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes.

[0080] The equivalent access impedance of each grid connection point is used as the input parameter. The grid connection points are classified according to the impedance weighting factor. Grid connection points with similar impedance weighting factors, that is, similar access impedance characteristics, are grouped into the same group.

[0081] The PQV model construction module is used to establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power, based on the connection impedance difference model. The specific method for obtaining the grid connection point PQV model containing connection impedance difference information is as follows: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now:

[0082] in, This is the equivalent voltage source voltage of the upstream power grid at the grid connection point. Further, its nonlinear PQV relationship can be obtained:

[0083] Impedance grouping The equivalent parameters for this group need to be calculated. The equivalent parameters are:

[0084] in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined. Based on these equivalent parameters, a group-level PQV model can be established:

[0085] The parameter correction module is used to input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the specific method of the grid connection point voltage-power relationship reflecting the current operating status as follows: By minimizing the error function:

[0086] in, For a moment At the grid connection point The actual voltage value measured at the location. The equivalent access impedance parameters are dynamically corrected to ensure that the model reflects the current operating state of the distribution network.

[0087] The voltage prediction and control decision module uses the updated grid connection point voltage-power relationship model to predict or perform sensitivity analysis on the grid connection point voltage, and outputs the response results of each grid connection point voltage to changes in active and reactive power. The specific method is as follows: With power regulation amount At that time, the predicted voltage at the grid connection point is:

[0088] in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value. This predicted value can inform operators in advance of the voltage change trend after power adjustment, providing a basis for whether to implement the adjustment plan. To meet voltage constraints. The required active power regulation is:

[0089] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0090] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for modeling the voltage-power relationship at the grid connection point of a distribution network, characterized in that, include: Step 1: Obtain the distribution network topology, line parameters, and transformer parameters, and collect voltage, active power, and reactive power operation data at each grid connection point; Step 2: Based on the distribution network topology and line parameters, calculate the equivalent access impedance between each grid connection point and the upper-level power grid to obtain the access impedance parameters that reflect the differences in electrical distance between different grid connection points; Step 3: Construct an access impedance difference model based on the access impedance parameters, and group or identify each grid connection point according to its access impedance characteristics; Step 4: Based on the aforementioned access impedance difference model, establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power to obtain the grid connection point PQV model containing access impedance difference information. Step 5: Input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the grid connection point voltage-power relationship that reflects the current operating status; Step 6: Using the updated grid connection point voltage-power relationship model, predict or perform sensitivity analysis on the grid connection point voltage, and output the response results of each grid connection point voltage to changes in active and reactive power. Step 2 includes: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance. : in, , Equivalent resistance , For equivalent reactance, Let k be the set of lines and transformers between the grid connection point and the upstream power grid. The index, j, is the imaginary unit; this access impedance is used to characterize the electrical distance of the grid connection point in the distribution network and its impact on voltage changes; Step 3 includes: An impedance weighting factor is introduced to characterize the proportional relationship between the active and reactive power effects on voltage: in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes. The equivalent access impedance of each grid connection point is used as the input parameter. The grid connection points are classified according to the impedance weighting factor. Grid connection points with similar access impedance characteristics within the preset range are grouped into the same group, and grid connection points with similar access impedance characteristics outside the preset range are divided into different groups. At the same time, the grid connection points in different groups are marked for model parameter correction and location in actual application. Step 4 includes: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now: in, The equivalent voltage source voltage of the upstream power grid at the grid connection point; For grid connection point The active power; For grid connection point reactive power; The voltage at grid connection point i The conjugate of complex numbers; Furthermore, its nonlinear PQV relationship is obtained: Take under normal operation Linearizing the above relationship to the first order, we get: in, , , These are the grid connection point voltage, active power, and reactive power changes, respectively. Define voltage sensitivity: This sensitivity parameter characterizes the voltage change caused by a unit change in active power or a unit change in reactive power. A larger sensitivity value indicates a more significant impact of the corresponding power change on the voltage. Simultaneously, to account for the influence of nonlinear factors, a second-order sensitivity is defined. When the photovoltaic output exceeds the load, that is ,but: Reverse power causes a voltage rise, and its over-limit condition is: in, This is the maximum allowable operating voltage at the grid connection point; This leads to the critical value for inverse power: in, For grid connection point The maximum reverse power allowed without voltage over-limit; when photovoltaic output reaches this critical value, power limiting measures are taken to avoid voltage over-limit; impedance grouping. Calculate the equivalent parameters of this group; the equivalent parameters are: in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined; based on these equivalent parameters, a PQV model at the group level is established: in, , , Impedance grouping The grid connection point voltage, active and reactive power changes; Step 5 includes: The equivalent access impedance parameters are dynamically corrected by minimizing the error function, so that the model reflects the current operating state of the distribution network. in, For a moment At the grid connection point The actual voltage value measured at the location; Step 6 includes: With power regulation amount At that time, the predicted voltage at the grid connection point is: in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value; To meet voltage constraints The required active power regulation is: The calculation results are directly applied to the operation and control of the distribution network. When the predicted voltage will exceed the upper limit, the distributed power generation is limited based on the calculated active power regulation, or the excess active power is absorbed by energy storage devices. At the same time, combined with reactive power regulation optimization, reactive power output is adjusted by reactive power compensation devices to ensure that the voltage remains stable within the allowable range.

2. A voltage-power relationship modeling system for distribution network connection points, characterized in that, It includes a data acquisition module, an access impedance calculation module, an impedance difference modeling module, a PQV model construction module, a parameter correction module, and a voltage prediction and control decision module; The data acquisition module is used to obtain the distribution network topology, line parameters and transformer parameters, and to collect voltage, active power and reactive power operation data of each grid connection point; The access impedance calculation module is used to calculate the equivalent access impedance between each grid connection point and the upper-level power grid based on the distribution network topology and line parameters, so as to obtain access impedance parameters that reflect the differences in electrical distance between different grid connection points. The impedance difference modeling module is used to construct an access impedance difference model based on the access impedance parameters, and to group or identify each grid connection point according to the access impedance characteristics. The PQV model construction module is used to establish a voltage-power relationship model between the voltage of each grid connection point and active and reactive power based on the access impedance difference model, so as to obtain a grid connection point PQV model containing access impedance difference information. The parameter correction module is used to input the real-time collected grid connection point voltage and power data into the PQV model, correct and update the model parameters, and obtain the grid connection point voltage-power relationship that reflects the current operating status. The voltage prediction and control decision module is used to predict or perform sensitivity analysis on the grid connection point voltage using the updated grid connection point voltage-power relationship model, and output the response results of each grid connection point voltage to changes in active and reactive power. The access impedance calculation module includes: For each grid connection point Based on the parameters of the lines and transformers it passes through to the upper-level power grid, calculate its equivalent connection impedance. : in, , Equivalent resistance , For equivalent reactance, Let k be the set of lines and transformers between the grid connection point and the upstream power grid. The index, j, is the imaginary unit; this access impedance is used to characterize the electrical distance of the grid connection point in the distribution network and its impact on voltage changes; The impedance difference modeling module includes: An impedance weighting factor is introduced to characterize the proportional relationship between the active and reactive power effects on voltage: in, For grid connection point The active impedance weighting factor is used to characterize the weighting of the effect of active power on voltage changes. For grid connection point The reactive impedance weighting factor is used to characterize the weighting of the impact of reactive power on voltage changes. The equivalent access impedance of each grid connection point is used as the input parameter. The grid connection points are classified according to the impedance weighting factor. Grid connection points with similar access impedance characteristics within the preset range are grouped into the same group, and grid connection points with similar access impedance characteristics outside the preset range are divided into different groups. At the same time, the grid connection points in different groups are marked for model parameter correction and location in actual application. The PQV model construction module includes: Grid connection point The complex power is set to Its current is The line voltage relationship is as follows ,Right now: in, The equivalent voltage source voltage of the upstream power grid at the grid connection point; For grid connection point The active power; For grid connection point reactive power; The voltage at grid connection point i The conjugate of complex numbers; Furthermore, its nonlinear PQV relationship is obtained: Take under normal operation Linearizing the above relationship to the first order, we get: in, , , These are the grid connection point voltage, active power, and reactive power changes, respectively. Define voltage sensitivity: This sensitivity parameter characterizes the voltage change caused by a unit change in active power or a unit change in reactive power. A larger sensitivity value indicates a more significant impact of the corresponding power change on the voltage. Simultaneously, to account for the influence of nonlinear factors, a second-order sensitivity is defined. When the photovoltaic output exceeds the load, that is ,but: Reverse power causes a voltage rise, and its over-limit condition is: in, This is the maximum allowable operating voltage at the grid connection point; This leads to the critical value for inverse power: in, For grid connection point The maximum reverse power allowed without voltage over-limit; when photovoltaic output reaches this critical value, power limiting measures are taken to avoid voltage over-limit; impedance grouping. Calculate the equivalent parameters of this group; the equivalent parameters are: in, This refers to a group of grid connection points with similar impedance characteristics. and Impedance grouping The equivalent resistance and equivalent reactance are determined; based on these equivalent parameters, a PQV model at the group level is established: in, , , Impedance grouping The grid connection point voltage, active and reactive power changes; The parameter correction module includes: The equivalent access impedance parameters are dynamically corrected by minimizing the error function, so that the model reflects the current operating state of the distribution network. in, For a moment At the grid connection point The actual voltage value measured at the location; The voltage prediction and control decision module includes: With power regulation amount At that time, the predicted voltage at the grid connection point is: in, The grid connection point is calculated based on the voltage-power relationship model at the grid connection point. The predicted voltage value; To meet voltage constraints The required active power regulation is: The calculation results are directly applied to the operation and control of the distribution network. When the predicted voltage will exceed the upper limit, the distributed power generation is limited based on the calculated active power regulation, or the excess active power is absorbed by energy storage devices. At the same time, combined with reactive power regulation optimization, reactive power output is adjusted by reactive power compensation devices to ensure that the voltage remains stable within the allowable range.

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