Power grid voltage stability evaluation method and device, storage medium and computer equipment

Abstract

The invention relates to the technical field of power distribution networks, and discloses a power grid voltage stability evaluation method and device, a storage medium and computer equipment, and the method comprises the steps: firstly determining a plurality of grid-connected points in a power distribution network system, constructing a corresponding voltage-reactive power model, and constructing a load flow calculation model of the power distribution network system; the method comprises the following steps: firstly, calculating a voltage-reactive power sensitivity value of each node, then solving power flows of a plurality of nodes in a model to obtain a sensitivity value of voltage-reactive power of each node, then identifying a reactive compensation position, calculating the capacity of a reactive compensation device by adopting a particle swarm optimization algorithm, finally, performing reactive compensation by utilizing the reactive compensation device, and evaluating a reactive compensation effect based on a preset rule. According to the method, the node which is most susceptible to influence under the condition of abnormal voltage is accurately identified, the dynamic relationship between the voltage and reactive power of each node is quantified, and accurate analysis of various power transmission systems is realized; the compensation effect is ensured in a complex multi-peak scene, the effectiveness of compensation measures is ensured, and the stability of a power distribution network system is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution networks, and in particular to a method, device, storage medium and computer equipment for evaluating power grid voltage stability. Background Art

[0002] With the continuous growth of global energy demand, various new energy transmission systems and multi-terminal high-voltage direct current transmission systems have been connected to the distribution network one after another. The stability of the power system is facing unprecedented challenges, especially under the complex interactions between direct current transmission systems, photovoltaic grid-connected and various transmission systems. How to effectively evaluate the stability of the receiving-end power grid when subjected to voltage anomalies has become a key issue in current power system research.

[0003] However, the existing grid voltage stability assessment methods are often unable to fully reflect the dynamic relationship between the voltage and reactive power of each node in the grid under the feeding conditions of renewable energy transmission systems and multi-terminal high-voltage direct current transmission systems. Therefore, it is difficult to accurately predict the vulnerable points of the distribution network, which in turn leads to the inability to provide sufficient theoretical basis for the reasonable configuration of reactive compensation devices. Summary of the invention

[0004] In view of this, the present application provides a method, device, storage medium and computer equipment for evaluating power grid voltage stability. The main purpose is to solve the technical problems in the prior art that the dynamic relationship between the voltage and reactive power of each node in the power grid cannot be grasped, the vulnerable points of the distribution network are difficult to predict, and the reactive compensation device cannot be reasonably configured.

[0005] According to a first aspect of the present invention, there is provided a method for evaluating power grid voltage stability, comprising:

[0006] Determine a plurality of grid connection points in the distribution network system, construct a voltage-reactive power model corresponding to each of the grid connection points, and construct a power flow calculation model of the distribution network system according to the plurality of voltage-reactive power models;

[0007] Acquire multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node;

[0008] The multiple sensitivity values ​​are sorted to identify the reactive power compensation location, and the capacity of the reactive power compensation device is calculated using a particle swarm optimization algorithm;

[0009] The reactive power compensation device is used to perform reactive power compensation at the reactive power compensation position, and the reactive power compensation effect is evaluated based on preset rules.

[0010] Optionally, the grid connection point includes a VSC-HVDC grid connection point; the determining of multiple grid connection points in the distribution network system and constructing a voltage-reactive power model corresponding to each of the grid connection points includes:

[0011] Determining a VSC-HVDC grid connection point in the distribution network system, wherein a receiving-end converter station of the VSC-HVDC grid connection point adopts fixed DC voltage control and fixed reactive power control;

[0012] When a ground fault occurs on the inverter side of the VSC-HVDC grid-connected point, the VSC-HVDC grid-connected point fluctuates and returns to a steady state. The active power and reactive power injected into the distribution network system by the receiving-end converter station of the VSC-HVDC grid-connected point in a steady state are respectively:

[0013]

[0014] Among them, P VSC is the active power delivered by the VSC-HVDC grid connection point; Q VSC is the reactive power transmitted by the VSC-HVDC grid connection point; U d_VSC is the d-axis component of the AC voltage at the VSC-HVDC grid connection point; U q_VSC is the q-axis component of the VSC-HVDC AC voltage; I d_VSC is the d-axis component of the AC current at the VSC-HVDC grid connection point; I q_VSC is the q-axis component of the VSC-HVDC AC current.

[0015] Optionally, the grid connection point includes a photovoltaic power generation system grid connection point, and the photovoltaic power generation system grid connection point includes a photovoltaic inverter and a direct-drive wind turbine grid-side converter; the determining of multiple grid connection points in the distribution network system and constructing a voltage-reactive power model corresponding to each of the grid connection points include:

[0016] When a fault occurs at the receiving end of the photovoltaic power generation system, a voltage-reactive power model corresponding to the grid-connected point of the photovoltaic power generation system is established, wherein the photovoltaic inverter and the grid-side converter of the direct-drive wind turbine adopt active and reactive decoupling dual-loop control after phase locking;

[0017] When a low voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter adopts an open-loop control strategy of a single current loop and provides reactive power support, wherein the reactive current is:

[0018] I T =K1(0.9-U T )I N

[0019] Where K1 is the low voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 1.5-2.5; UT is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing;

[0020] When a high voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter absorbs reactive power and increases the DC side voltage reference value, wherein the reactive current is:

[0021] I T =K2(1.1-U T )I N

[0022] Where K2 is the high voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 0 to 1.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing;

[0023] When the voltage fluctuates, the power generated by the photovoltaic power generation system is:

[0024]

[0025] P pv =P ref

[0026] In the formula, Q pv is the reactive power of the photovoltaic power generation system; U pv is the AC voltage of the photovoltaic power generation system; I pv is the AC current of the photovoltaic power generation system; P pv is the active power delivered by the photovoltaic power generation system; P ref is the reference value of active power delivered by the photovoltaic power generation system; Q ref It is the reference value of reactive power delivered by the photovoltaic power generation system.

[0027] Optionally, the acquiring multiple node flows in the flow calculation model and solving the node flows to obtain a voltage-reactive power sensitivity value of each node includes:

[0028] Select a target node from multiple node flows, add reactive power change to the target node, and calculate voltage change of each node except the target node;

[0029] Based on the voltage variation of each remaining node and the reactive power variation of the target node, a voltage-reactive power sensitivity value of each remaining node is determined.

[0030] Optionally, after acquiring multiple node flows in the flow calculation model and solving the node flows to obtain a voltage-reactive power sensitivity value of each node, the method further includes:

[0031] Obtaining a system node impedance matrix of the power flow calculation model;

[0032] When the distribution network system fails and the voltage of each node in the power flow calculation model changes, the system node impedance matrix is ​​corrected using the branch addition method.

[0033] Optionally, the method of identifying a reactive compensation position based on sorting a plurality of sensitivity values ​​and calculating the capacity of the reactive compensation device using a particle swarm optimization algorithm includes:

[0034] Sorting multiple sensitivity values ​​and identifying weak nodes, and determining reactive power compensation positions according to the weak nodes;

[0035] The position and speed of the particle group are determined based on the reactive power compensation position, and the capacity of the reactive power compensation device is calculated according to the position and speed of the particle group.

[0036] Optionally, the evaluating the reactive power compensation effect based on a preset rule includes:

[0037] constructing a multi-binary table based on a preset voltage drop threshold and a maximum acceptable duration corresponding to the voltage drop threshold;

[0038] Recording voltage change data after disturbance occurs at each reactive compensation position after reactive compensation, wherein the voltage change data includes a voltage drop value and a voltage drop duration;

[0039] Matching the voltage change data with the multi-binary table to obtain a weight corresponding to each voltage change data, and integrating the weight to obtain a total score;

[0040] A quantitative evaluation index is constructed according to the total score corresponding to each voltage change data, wherein the quantitative evaluation index is used to evaluate the reactive power compensation effect.

[0041] According to a second aspect of the present invention, there is provided a power grid voltage stability assessment device, the device comprising:

[0042] A model building module, used to determine a plurality of grid connection points in a distribution network system, construct a voltage-reactive power model corresponding to each of the grid connection points, and construct a power flow calculation model of the distribution network system according to the plurality of voltage-reactive power models;

[0043] A sensitivity calculation module, used to obtain multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node;

[0044] A reactive compensation calculation module, for identifying a reactive compensation position based on sorting a plurality of sensitivity values, and calculating the capacity of a reactive compensation device using a particle swarm optimization algorithm;

[0045] The compensation effect evaluation module is used to use the reactive compensation device to perform reactive compensation at the reactive compensation position, and evaluate the reactive compensation effect based on preset rules.

[0046] According to a third aspect of the present invention, there is provided a storage medium having a computer program stored thereon, and when the program is executed by a processor, the above-mentioned method for evaluating power grid voltage stability is implemented.

[0047] According to a fourth aspect of the present invention, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the above-mentioned grid voltage stability assessment method is implemented when the processor executes the program.

[0048] The power grid voltage stability evaluation method, device, storage medium and computer equipment provided by the present invention first determine multiple grid connection points in the distribution network system, construct a voltage-reactive power model corresponding to each grid connection point, and construct a power flow calculation model of the distribution network system according to the multiple voltage-reactive power models. Then, multiple node flows in the power flow calculation model are obtained, and the node flows are solved to obtain the voltage-reactive power sensitivity value of each node. Then, the multiple sensitivity values ​​are sorted to identify the reactive compensation position, and the capacity of the reactive compensation device is calculated by using a particle swarm optimization algorithm. Finally, the reactive compensation device is used to perform reactive compensation at the reactive compensation position, and the reactive compensation effect is evaluated based on preset rules. The above method establishes a voltage-reactive power model for each grid connection point, and then constructs a power flow calculation model for the entire distribution network, accurately simulating the system behavior under different operating conditions, which helps to accurately identify the nodes that are most susceptible to voltage abnormalities; the sensitivity value of voltage-reactive power obtained by solving the node power flow can quantify the dynamic relationship between the voltage and reactive power of each node, and realize accurate analysis of the complex interaction of various transmission systems; the particle swarm optimization algorithm is used to calculate the optimal capacity of the reactive compensation device, and the compensation effect is evaluated after the reactive compensation is implemented, so as to ensure the compensation effect in complex multi-peak scenarios, ensure the effectiveness of compensation measures, and enhance the stability of the distribution network system.

[0049] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0051] Figure 1 A schematic diagram of a flow chart of a method for evaluating power grid voltage stability provided by an embodiment of the present invention is shown;

[0052] Figure 2 A schematic diagram of the structure of a power grid voltage stability assessment device provided by an embodiment of the present invention is shown;

[0053] Figure 3 A schematic diagram showing the structure of another power grid voltage stability assessment device provided by an embodiment of the present invention is shown;

[0054] Figure 4 A schematic diagram of the device structure of a computer device provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0055] The exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0056] In one embodiment, Figure 1 As shown, a method for evaluating power grid voltage stability is provided, comprising the following steps:

[0057] 101. Determine multiple grid connection points in the distribution network system, construct a voltage-reactive power model corresponding to each grid connection point, and construct a power flow calculation model of the distribution network system based on the multiple voltage-reactive power models.

[0058] Specifically, it is necessary to identify all possible grid connection points in the distribution network, that is, the places where new energy power generation equipment, energy storage systems or other types of distributed power sources are connected to the main power grid. For each identified grid connection point, it is necessary to construct a mathematical model that describes the relationship between the voltage at that point and the injected or absorbed reactive power. This model is usually based on a node admittance matrix or a more complex set of nonlinear equations, depending on the type and characteristics of the grid connection point. Once the voltage-reactive power model of each grid connection point is established, all nodes and models can be integrated into a comprehensive power flow calculation model of the distribution network system. The power flow calculation model accurately reflects the overall model of the flow of electric energy in the entire system.

[0059] In this embodiment, constructing a detailed voltage-reactive power model can capture the unique dynamic behavior at the grid connection point, so that the final power flow calculation model is closer to the actual situation, thereby improving the prediction accuracy; this application not only considers each grid connection point individually, but also integrates the grid connection points into a larger framework, which helps to deeply understand the interaction between different grid connection points. The power flow calculation model not only includes the relationship between directly connected grid connection points, but also covers the indirect impact between long-distance grid connection points, thereby improving data processing accuracy.

[0060] 102. Obtain multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node.

[0061] Specifically, based on different operating conditions, the power flow of each node is obtained by performing power flow calculation on the power flow calculation model of the distribution network system. The node power flow specifically includes data information such as active power, reactive power, current and voltage values; then, appropriate algorithms, such as the Newton-Raphson method, the Gauss-Seidel iteration method, etc., are used to solve the power flow equation to obtain the specific operating parameters of each node. The solution process usually requires repeated iterations until the convergence criteria are met to ensure the accuracy of the results; then for each node, the rate of change of its voltage change relative to the injected or absorbed reactive power is analyzed, that is, the voltage-reactive power sensitivity value. The sensitivity value reflects how the voltage of a node and possibly other related nodes will respond when the reactive power of a node changes under specific conditions.

[0062] In this embodiment, the calculated sensitivity value can clearly quantify the interaction between voltage and reactive power between nodes, providing a quantitative method to evaluate the behavior of the distribution network system under different voltage change conditions, which is very important for understanding and predicting complex interactions; and by obtaining the sensitivity value of voltage-reactive power, key nodes can be identified, which plays an important role in the subsequent accurate identification of the most sensitive and vulnerable nodes in the distribution network system.

[0063] 103. Sort multiple sensitivity values ​​to identify reactive power compensation locations, and use a particle swarm optimization algorithm to calculate the capacity of the reactive power compensation device.

[0064] Specifically, by sorting the voltage-reactive power sensitivity values ​​of all nodes, we can identify those nodes that have the greatest impact on voltage when reactive power changes, that is, select several key nodes that most need reactive compensation from the sorting results as candidate locations. Candidate locations are usually points with high sensitivity values, that is, they are most sensitive to voltage fluctuations. In addition to the sensitivity value, other factors such as cost-benefit analysis and geographical distribution balance may also be combined to finally determine the compensation location; then define a particle for each selected compensation location, each particle represents a set of possible reactive compensation device configurations, including type, quantity and capacity, and construct a fitness function to evaluate the effect of each group of configurations, such as minimizing the total network loss of the system, keeping the voltage stable within the specified range, maximizing economic benefits, etc. Finally, use the particle swarm optimization algorithm to update the position of the particles through multiple iterations until the global optimal solution is found or the predetermined stop condition is reached.

[0065] In this embodiment, by sorting the sensitivity values, the most vulnerable nodes in the system can be accurately found, ensuring that resources are concentrated in the most critical places, thereby effectively improving the stability of the overall system; the particle swarm optimization algorithm, as an efficient global search method, can quickly find near-optimal solutions in complex nonlinear problem spaces, avoiding the inefficiency and uncertainty of traditional trial and error methods; by comprehensively considering multiple factors to select the compensation position, and using the particle swarm optimization algorithm to accurately calculate the compensation capacity, the optimal allocation of resources is achieved, and the particle swarm optimization allows dynamic adjustment of the reactive compensation strategy, and can flexibly change the settings of the compensation device according to the actual operating status of the power grid to adapt to changing needs.

[0066] 104. Perform reactive power compensation at a reactive power compensation location using a reactive power compensation device, and evaluate the reactive power compensation effect based on preset rules.

[0067] Specifically, according to the optimal capacity and location information calculated in the previous steps, select a suitable reactive compensation device, such as a static VAR compensator SVC, a static synchronous compensator STATCOM, a capacitor bank, etc., install the selected reactive compensation device on the determined key nodes to implement reactive compensation, activate the reactive compensation device to provide or absorb the required reactive power to the power grid to maintain a stable voltage level, and automatically adjust the reactive compensation amount according to the real-time monitoring data to ensure optimal performance. Finally, establish a scientific and reasonable evaluation system to evaluate the compensation effect. If the compensation effect is not satisfactory, timely adjustments can be made.

[0068] In this embodiment, by precisely controlling the flow of reactive power, voltage fluctuations can be effectively alleviated and power supply reliability can be improved. Especially when the load changes frequently or a large number of distributed energy sources are connected, optimized reactive compensation helps to reduce energy losses in the transmission and distribution process, thereby improving the transmission efficiency of the entire system and saving operating costs; stable voltage levels reduce the risk of failures caused by voltage anomalies and enhance the overall stability and safety of the distribution network system.

[0069] The grid voltage stability assessment method provided in the present embodiment first determines multiple grid connection points in the distribution network system, constructs a voltage-reactive power model corresponding to each grid connection point, constructs a power flow calculation model of the distribution network system according to the multiple voltage-reactive power models, then obtains multiple node power flows in the power flow calculation model, and solves the node power flows to obtain the voltage-reactive power sensitivity value of each node, then sorts the multiple sensitivity values ​​to identify the reactive compensation position, and uses a particle swarm optimization algorithm to calculate the capacity of the reactive compensation device, and finally uses the reactive compensation device to perform reactive compensation at the reactive compensation position, and evaluates the reactive compensation effect based on preset rules. The above method establishes a voltage-reactive power model for each grid connection point, and then constructs a power flow calculation model for the entire distribution network, accurately simulating the system behavior under different operating conditions, which helps to accurately identify the nodes that are most susceptible to voltage abnormalities; the sensitivity value of voltage-reactive power obtained by solving the node power flow can quantify the dynamic relationship between the voltage and reactive power of each node, and realize accurate analysis of the complex interaction of various transmission systems; the particle swarm optimization algorithm is used to calculate the optimal capacity of the reactive compensation device, and the compensation effect is evaluated after the reactive compensation is implemented, so as to ensure the compensation effect in complex multi-peak scenarios, ensure the effectiveness of compensation measures, and enhance the stability of the distribution network system.

[0070] In an optional implementation, step 101 may be implemented in the following manner:

[0071] It should be noted that, considering the application scenarios of the present application, the distribution network system includes multiple grid-connected points, such as LCC-HVDC grid-connected points, VSC-HVDC grid-connected points, new energy system grid-connected points, induction motor load grid-connected points, and constant impedance load grid-connected points. Among them, the voltage-reactive power model construction method of LCC-HVDC grid-connected points, induction motor load grid-connected points and constant impedance load grid-connected points belongs to the prior art and has been disclosed. The present application does not go into details about this. Therefore, the present application specifically describes the voltage-reactive power model establishment process of the VSC-HVDC grid-connected points and the photovoltaic power generation system in the new energy system.

[0072] The process of establishing the voltage-reactive power model of the VSC-HVDC grid connection point is as follows:

[0073] When the VSC-HVDC receiving-end converter station adopts constant DC voltage control and constant reactive power control, after a ground fault occurs on the inverter side, the flexible DC transmission will fluctuate. The active power and reactive power injected into the AC system by the converter in steady state are:

[0074]

[0075] Among them, P VSC is the active power delivered by the VSC-HVDC grid connection point; Q VSC is the reactive power transmitted by the VSC-HVDC grid connection point; U d_VSC is the d-axis component of the AC voltage at the VSC-HVDC grid connection point; U q_VSC is the q-axis component of the VSC-HVDC AC voltage; I d_VSC is the d-axis component of the AC current at the VSC-HVDC grid connection point; I q_VSC is the q-axis component of the VSC-HVDC AC current.

[0076] Among them, the process of establishing the voltage-reactive power model of the photovoltaic power generation system grid connection point is as follows:

[0077] When the new energy station adopts photovoltaic power generation system, the grid-connected point voltage-reactive power model is obtained based on the fact that when a fault occurs at the receiving end, the active power and reactive power of the photovoltaic power generation system are affected by low voltage ride-through control and AC voltage changes. For photovoltaic inverters (PVI) and direct-drive wind turbine grid-side converters (GSC), active and reactive decoupling dual-loop control after phase locking is usually adopted. When a low voltage fault occurs in the system, the grid-connected inverter switches the control mode and adopts a single current loop open-loop control strategy, while providing certain reactive power support. The reactive current requirements are as follows:

[0078] I T =K1(0.9-U T )I N

[0079] In the formula, K1 ranges from 1.5 to 2.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing.

[0080] When a high voltage fault occurs in the system, the grid-connected inverter also needs to switch the control mode but does not disconnect from the grid within a certain period of time. However, unlike the low voltage fault, the high voltage ride-through fault requires the grid-connected inverter to absorb reactive power. At the same time, the DC side voltage reference value is usually increased to stabilize the DC side voltage fluctuation during the high voltage ride-through period. The reactive current requirements are as follows:

[0081] I T =K2(1.1-U T )I N

[0082] In the formula, the value range of K2 is 0 to 1.5.

[0083] When the voltage fluctuates, the power generated by photovoltaic is:

[0084]

[0085] P pv =P ref

[0086] Among them, Q pv is the reactive power of the photovoltaic power generation system; U pv is the AC voltage of the photovoltaic power generation system; I pv is the AC current of the photovoltaic power generation system; K1 is the low voltage ride-through coefficient of the photovoltaic power generation system; K2 is the low voltage ride-through coefficient of the photovoltaic power generation system; P pv is the active power delivered by the photovoltaic power generation system; P ref is the reference value of active power delivered by the photovoltaic power generation system; Q ref It is the reference value of reactive power delivered by the photovoltaic power generation system.

[0087] In an optional implementation, step 102 may be implemented in the following manner:

[0088] A target node is selected from multiple node flows, reactive power changes are added to the target node, and the voltage changes of each node except the target node are calculated; based on the voltage changes of each remaining node and the reactive power changes of the target node, the voltage-reactive power sensitivity value of each remaining node is determined.

[0089] In this embodiment, the elements of the sensitivity matrix can be solved by making a small disturbance to each node and calculating the voltage change. For example, a certain value of reactive power △Q is added to a node j to calculate the change value of the voltage of the remaining nodes i. The change value of the voltage of a node i divided by the change amount of the reactive power of node j is the sensitivity between the voltage of node i and node j. The calculation formula is:

[0090]

[0091] In the formula, is the sensitivity between the voltage at node i and node j, U i_f To set the voltage value after adding reactive power disturbance, U i_0 The voltage value before adding the reactive power disturbance to the setting.

[0092] In another embodiment, after obtaining the relationship between the voltage and reactive power of each node in the distribution network, it is assumed that the voltage of all nodes is known, and the influence of the change in voltage phase angle is ignored, and it is set as a constant, and then the direct power flow method is used to solve the voltage-reactive power sensitivity of each node.

[0093] In an optional embodiment, the grid voltage stability assessment method further includes step 105, namely, after obtaining the voltage-reactive power sensitivity value of each node, obtaining the system node impedance matrix of the power flow calculation model; when a fault occurs in the distribution network system and the voltage of each node in the power flow calculation model changes, the system node impedance matrix is ​​corrected using the branch addition method.

[0094] In this embodiment, when a fault occurs in the distribution network system, the voltage of each node will suddenly change. The key reason is the change in the network structure and the electrical connection between each node caused by the fault, which is manifested as a change in the impedance matrix of the system node. The change in the network structure caused by the fault affects the voltage support capacity of the power supply to each node of the network, causing the voltage of each node to decrease. The more critical the position of the node in the network, the greater the impact on the grid voltage when it fails.

[0095] When the network structure changes, the original matrix can be directly modified by the branch addition method to obtain the node impedance matrix in the new state, avoiding the work of recalculating the entire matrix. Specifically, for the system node impedance matrix Z, when a ground branch with impedance z is added at node k, the new node impedance matrix is:

[0096]

[0097] Where Z is the system node impedance matrix; represents the modified node impedance matrix, z k is the impedance value of the added branch; M k It represents the association vector of the newly added ground branch at node k, and its usual structure is M k =[0,...·,0,1,0,...,0];N k M k The transpose of

[0098] When a three-phase metallic short circuit fault occurs at a network node k, it can be equivalent to adding a z k = 0 for the ground branch, we can get:

[0099]

[0100] Where k is the node number where the fault occurs, Z kk Represents an element in the nodal impedance matrix.

[0101] In an optional implementation, step 103 may be implemented in the following manner:

[0102] The particle swarm optimization algorithm is used to evaluate the reactive power that the reactive compensation device should compensate. First, the position and velocity of the particle swarm are initialized. The position x of each particle is ij represents the sensitivity value of the i-th particle at the j-th node, and the particle's velocity v ij It indicates the direction and amplitude of the change of reactive compensation, which can be expressed as:

[0103]

[0104] Among them, the flight speed limit of the particle is generally set to 20%-40% of the search space; c1 and c2 are non-negative constants, also known as learning factors, which usually have the same value and are between [0, 4]; r1 and r2 are arbitrary constants between 0 and 1; w is the inertia weight coefficient; x ij pb (t) is the optimal position of the particle at that moment.

[0105] In an optional implementation, step 104 may be implemented in the following manner:

[0106] In order to accurately evaluate the transient voltage compensation effect of the power system, a quantitative evaluation index is needed to evaluate whether the transient voltage of each node in the distribution network system is unstable. This application specifically adopts the specified voltage drop threshold and the corresponding maximum acceptable duration to construct a (Ver, Ter) multi-binary table. Based on the multi-binary table, the transient voltage data is weighted and integrated according to different voltage drop degrees, thereby constructing a transient voltage stability quantitative evaluation index:

[0107]

[0108] Where i and j are the corresponding time interval and voltage interval numbers respectively; g(i, j) is used to determine the voltage interval where a point on the transient voltage curve is located; V N is the rated voltage of the busbar; K j is the weight coefficient when the voltage is in the interval [Vcr, j+1, Vcr]. The deeper the drop and the shorter the maximum acceptable duration, the greater the corresponding weight.

[0109] The quantitative index η defined above characterizes the transient voltage stability margin of the bus. When η>0, it indicates that the bus transient voltage is stable, and η<0 indicates that the bus transient voltage is unstable. This index can effectively reflect the severity of transient voltage drop and the risk of instability. Then, based on this quantitative index, the compensation effect of the dynamic reactive power device is evaluated, and then the dynamic reactive power optimization configuration scheme can be explored.

[0110] Further, as Figure 1 The specific implementation of the method shown in the embodiment provides a power grid voltage stability assessment device, such as Figure 2 As shown, the device includes: a model building module 201, a sensitivity calculation module 202, a reactive power compensation calculation module 203 and a compensation effect evaluation module 204, wherein:

[0111] The model building module 201 is used to determine a plurality of grid connection points in the distribution network system, construct a voltage-reactive power model corresponding to each of the grid connection points, and construct a power flow calculation model of the distribution network system according to the plurality of voltage-reactive power models;

[0112] The sensitivity calculation module 202 is used to obtain multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node;

[0113] A reactive compensation calculation module 203, for identifying a reactive compensation position based on sorting a plurality of sensitivity values, and calculating the capacity of a reactive compensation device using a particle swarm optimization algorithm;

[0114] The compensation effect evaluation module 204 is used to use the reactive compensation device to perform reactive compensation at the reactive compensation position, and evaluate the reactive compensation effect based on preset rules.

[0115] In a specific application scenario, the grid connection point includes a VSC-HVDC grid connection point; the model building module 201 can be specifically used to determine the VSC-HVDC grid connection point in the distribution network system, wherein the receiving-end converter station of the VSC-HVDC grid connection point adopts fixed DC voltage control and fixed reactive power control;

[0116] When a ground fault occurs on the inverter side of the VSC-HVDC grid-connected point, the VSC-HVDC grid-connected point fluctuates and returns to a steady state. The active power and reactive power injected into the distribution network system by the receiving-end converter station of the VSC-HVDC grid-connected point in a steady state are respectively:

[0117]

[0118] Among them, P VSC is the active power delivered by the VSC-HVDC grid connection point; Q VSC is the reactive power transmitted by the VSC-HVDC grid connection point; U d_VSC is the d-axis component of the AC voltage at the VSC-HVDC grid connection point; U q_VSC is the q-axis component of the VSC-HVDC AC voltage; I d_VSC is the d-axis component of the AC current at the VSC-HVDC grid connection point; Iq_VSC is the q-axis component of the VSC-HVDC AC current.

[0119] In a specific application scenario, the grid-connected point includes a photovoltaic power generation system grid-connected point, and the photovoltaic power generation system grid-connected point includes a photovoltaic inverter and a direct-drive wind turbine grid-side converter; the model establishment module 201 can be specifically used to establish a voltage-reactive power model corresponding to the photovoltaic power generation system grid-connected point when a fault occurs at the receiving end of the photovoltaic power generation system, wherein the photovoltaic inverter and the direct-drive wind turbine grid-side converter adopt active and reactive decoupling dual-loop control after phase locking;

[0120] When a low voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter adopts an open-loop control strategy of a single current loop and provides reactive power support, wherein the reactive current is:

[0121] I T =K1(0.9-U T )I N

[0122] Where K1 is the low voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 1.5-2.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing;

[0123] When a high voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter absorbs reactive power and increases the DC side voltage reference value, wherein the reactive current is:

[0124] I T =K2(1.1-U T )I N

[0125] Where K2 is the high voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 0 to 1.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing;

[0126] When the voltage fluctuates, the power generated by the photovoltaic power generation system is:

[0127]

[0128] P pv =P ref

[0129] In the formula, Q pv is the reactive power of the photovoltaic power generation system; U pv is the AC voltage of the photovoltaic power generation system; I pvis the AC current of the photovoltaic power generation system; P pv is the active power delivered by the photovoltaic power generation system; P ref is the reference value of active power delivered by the photovoltaic power generation system; Q ref It is the reference value of reactive power delivered by the photovoltaic power generation system.

[0130] In a specific application scenario, the sensitivity calculation module 202 can be used to select a target node from multiple node flows, add a reactive power change to the target node, and calculate the voltage change of each node except the target node; based on the voltage change of each remaining node and the reactive power change of the target node, determine the voltage-reactive power sensitivity value of each remaining node.

[0131] In specific application scenarios, such as Figure 3 As shown, the device also includes a matrix correction module 205, which can be specifically used to obtain the system node impedance matrix of the power flow calculation model; when the distribution network system fails and the voltage of each node in the power flow calculation model changes, the system node impedance matrix is ​​corrected using the branch addition method.

[0132] In a specific application scenario, the reactive power compensation calculation module 203 can be used to sort multiple sensitivity values ​​and identify weak nodes, determine the reactive power compensation position based on the weak nodes; determine the position and speed of the particle group based on the reactive power compensation position, and calculate the capacity of the reactive power compensation device based on the position and speed of the particle group.

[0133] In a specific application scenario, the compensation effect evaluation module 204 can be specifically used to construct a multi-binary table based on a preset voltage drop threshold and the maximum acceptable duration corresponding to the voltage drop threshold; record the voltage change data after disturbance occurs at each reactive compensation position after reactive compensation, wherein the voltage change data includes a voltage drop value and a voltage drop duration; match the voltage change data with the multi-binary table to obtain a weight corresponding to each voltage change data, and integrate the weight to obtain a total score; construct a quantitative evaluation index according to the total score corresponding to each voltage change data, wherein the quantitative evaluation index is used to evaluate the reactive compensation effect.

[0134] It should be noted that for other corresponding descriptions of the functional units involved in the power grid voltage stability assessment device provided in this embodiment, reference can be made to Figure 1 The corresponding description in will not be repeated here.

[0135] Based on the above Figure 1The method shown, accordingly, this embodiment also provides a storage medium, on which a computer program is stored, and when the program is executed by a processor, the above-mentioned power grid voltage stability evaluation method is implemented.

[0136] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product. The software product to be identified can be stored in a non-volatile storage medium (which can be a CD-ROM, USB flash drive, mobile hard disk, etc.), including a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute the grid voltage stability assessment method in each implementation scenario of the present application.

[0137] Based on the above Figure 1 The method shown, and Figure 2 and Figure 3 The power grid voltage stability assessment device shown in the figure is used to achieve the above-mentioned purpose. Figure 4 As shown, this embodiment also provides a physical device for evaluating the voltage stability of a power grid, which includes a communication bus, a processor, a memory, and a communication interface, and may also include an input and output interface and a display device, wherein each functional unit can communicate with each other through the bus. The memory stores a computer program, and the processor is used to execute the program stored in the memory and execute the method for evaluating the voltage stability of a power grid in the above embodiment.

[0138] Optionally, the physical device may also include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a WI-FI interface), etc.

[0139] Those skilled in the art will appreciate that the structure of a grid voltage stability assessment entity device provided in this embodiment does not constitute a limitation on the entity device, and may include more or fewer components, or a combination of certain components, or different component arrangements.

[0140] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages the hardware of the physical device and the software resources to be identified, and supports the operation of the information processing program and other software and / or programs to be identified. The network communication module is used to realize the communication between the components inside the storage medium, and the communication with other hardware and software in the information processing physical device.

[0141] Through the description of the above implementation methods, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform, or by hardware. First, multiple grid connection points in the distribution network system are determined, a voltage-reactive power model corresponding to each grid connection point is constructed, and a flow calculation model of the distribution network system is constructed according to multiple voltage-reactive power models. Then, multiple node flows in the flow calculation model are obtained, and the node flows are solved to obtain the voltage-reactive power sensitivity value of each node. Then, multiple sensitivity values ​​are sorted to identify the reactive compensation position, and a particle swarm optimization algorithm is used to calculate the capacity of the reactive compensation device. Finally, the reactive compensation device is used to perform reactive compensation at the reactive compensation position, and the reactive compensation effect is evaluated based on preset rules. The above method establishes a voltage-reactive power model for each grid connection point, and then constructs a power flow calculation model for the entire distribution network, accurately simulating the system behavior under different operating conditions, which helps to accurately identify the nodes that are most susceptible to voltage abnormalities; the sensitivity value of voltage-reactive power obtained by solving the node power flow can quantify the dynamic relationship between the voltage and reactive power of each node, and realize accurate analysis of the complex interaction of various transmission systems; the particle swarm optimization algorithm is used to calculate the optimal capacity of the reactive compensation device, and the compensation effect is evaluated after the reactive compensation is implemented, so as to ensure the compensation effect in complex multi-peak scenarios, ensure the effectiveness of compensation measures, and enhance the stability of the distribution network system.

[0142] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. Those skilled in the art will appreciate that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be changed accordingly and located in one or more devices different from the present implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple submodules.

[0143] The above serial numbers of this application are only for description and do not represent the advantages and disadvantages of the implementation scenarios. The above disclosure is only a few specific implementation scenarios of this application, but this application is not limited to them, and any changes that can be thought of by technicians in this field should fall within the scope of protection of this application.

Claims

1. A method for evaluating power grid voltage stability, characterized in that: include: Determine a plurality of grid connection points in the distribution network system, construct a voltage-reactive power model corresponding to each of the grid connection points, and construct a power flow calculation model of the distribution network system according to the plurality of voltage-reactive power models; Acquire multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node; The multiple sensitivity values ​​are sorted to identify the reactive power compensation location, and the capacity of the reactive power compensation device is calculated using a particle swarm optimization algorithm; The reactive power compensation device is used to perform reactive power compensation at the reactive power compensation position, and the reactive power compensation effect is evaluated based on preset rules.

2. The method according to claim 1, characterized in that The grid connection point includes a VSC-HVDC grid connection point; the determining of multiple grid connection points in the distribution network system and constructing a voltage-reactive power model corresponding to each of the grid connection points include: Determining a VSC-HVDC grid connection point in the distribution network system, wherein a receiving-end converter station of the VSC-HVDC grid connection point adopts fixed DC voltage control and fixed reactive power control; When a ground fault occurs on the inverter side of the VSC-HVDC grid-connected point, the VSC-HVDC grid-connected point fluctuates and returns to a steady state. The active power and reactive power injected into the distribution network system by the receiving-end converter station of the VSC-HVDC grid-connected point in a steady state are respectively: Among them, P VSC is the active power delivered by the VSC-HVDC grid connection point; Q VSC is the reactive power transmitted by the VSC-HVDC grid connection point; U d_VSC is the d-axis component of the AC voltage at the VSC-HVDC grid connection point; U q_VSC is the q-axis component of the VSC-HVDC AC voltage; I d_VSC is the d-axis component of the AC current at the VSC-HVDC grid connection point; I q_VSC is the q-axis component of the VSC-HVDC AC current.

3. The method according to claim 1, characterized in that The grid connection point includes a photovoltaic power generation system grid connection point, and the photovoltaic power generation system grid connection point includes a photovoltaic inverter and a direct-drive wind turbine grid-side converter; the determining of multiple grid connection points in the distribution network system and constructing a voltage-reactive power model corresponding to each of the grid connection points include: When a fault occurs at the receiving end of the photovoltaic power generation system, a voltage-reactive power model corresponding to the grid-connected point of the photovoltaic power generation system is established, wherein the photovoltaic inverter and the grid-side converter of the direct-drive wind turbine adopt active and reactive decoupling dual-loop control after phase locking; When a low voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter adopts an open-loop control strategy of a single current loop and provides reactive power support, wherein the reactive current is: AND T =K1(0.9-U T )AND N Where K1 is the low voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 1.5-2.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing; When a high voltage fault occurs in the photovoltaic power generation system, the photovoltaic inverter absorbs reactive power and increases the DC side voltage reference value, wherein the reactive current is: I T =K2(1.1-U T )I N Where K2 is the high voltage ride-through coefficient of the photovoltaic power generation system, and its value range is 0 to 1.5; U T is the actual current of the photovoltaic power generation system during the crossing; I N It is the rated current of the photovoltaic power generation system during the crossing; When the voltage fluctuates, the power generated by the photovoltaic power generation system is: P pv =P ref In the formula, Q pv is the reactive power of the photovoltaic power generation system; U pv is the AC voltage of the photovoltaic power generation system; I pv is the AC current of the photovoltaic power generation system; P pv is the active power delivered by the photovoltaic power generation system; P ref is the reference value of active power delivered by the photovoltaic power generation system; Q ref It is the reference value of reactive power delivered by the photovoltaic power generation system.

4. The method according to claim 1, characterized in that: The step of obtaining multiple node flows in the flow calculation model and solving the node flows to obtain a voltage-reactive power sensitivity value of each node includes: Select a target node from multiple node flows, add reactive power change to the target node, and calculate voltage change of each node except the target node; Based on the voltage variation of each remaining node and the reactive power variation of the target node, a voltage-reactive power sensitivity value of each remaining node is determined.

5. The method according to claim 1, characterized in that After obtaining multiple node flows in the flow calculation model and solving the node flows to obtain the voltage-reactive power sensitivity value of each node, the method further includes: Obtaining a system node impedance matrix of the power flow calculation model; When the distribution network system fails and the voltage of each node in the power flow calculation model changes, the system node impedance matrix is ​​corrected using the branch addition method.

6. The method according to claim 1, characterized in that The method of sorting the plurality of sensitivity values ​​to identify the reactive power compensation position and using the particle swarm optimization algorithm to calculate the capacity of the reactive power compensation device includes: Sorting multiple sensitivity values ​​and identifying weak nodes, and determining reactive power compensation positions according to the weak nodes; The position and speed of the particle group are determined based on the reactive power compensation position, and the capacity of the reactive power compensation device is calculated according to the position and speed of the particle group.

7. The method according to claim 1, characterized in that The evaluating the reactive power compensation effect based on the preset rules includes: constructing a multi-binary table based on a preset voltage drop threshold and a maximum acceptable duration corresponding to the voltage drop threshold; Recording voltage change data after disturbance occurs at each reactive compensation position after reactive compensation, wherein the voltage change data includes a voltage drop value and a voltage drop duration; Matching the voltage change data with the multi-binary table to obtain a weight corresponding to each voltage change data, and integrating the weight to obtain a total score; A quantitative evaluation index is constructed according to the total score corresponding to each voltage change data, wherein the quantitative evaluation index is used to evaluate the reactive power compensation effect.

8. A power grid voltage stability assessment device, characterized in that: The device comprises: A model building module, used to determine a plurality of grid connection points in a distribution network system, construct a voltage-reactive power model corresponding to each of the grid connection points, and construct a power flow calculation model of the distribution network system according to the plurality of voltage-reactive power models; A sensitivity calculation module, used to obtain multiple node flows in the flow calculation model, and solve the node flows to obtain the voltage-reactive power sensitivity value of each node; A reactive compensation calculation module is used to sort multiple sensitivity values ​​to identify reactive compensation positions and calculate the capacity of reactive compensation devices using a particle swarm optimization algorithm; The compensation effect evaluation module is used to use the reactive compensation device to perform reactive compensation at the reactive compensation position, and evaluate the reactive compensation effect based on preset rules.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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