Reactive voltage hierarchical regulation and control method, device and equipment suitable for wind field SVG (Static Var Generator)

Abstract

The invention provides a reactive voltage hierarchical regulation and control method, device and equipment suitable for a wind field SVG, and relates to the technical field of new energy grid connection and reactive voltage coordination control. The method comprises the following steps: obtaining a fitting equation of reactive power demand and power grid voltage and adjusting sensitivity of each equivalent wind field to wind power plant grid-connected point voltage; if the real-time wind power plant grid-connected point voltage is lower than the voltage drop threshold value and the SVG does not reach the reactive power upper limit, determining the current reactive power demand according to the real-time power grid voltage and the fitting equation so as to start the SVG to carry out primary reactive power support; and if the real-time voltage of the grid-connected point of the wind power plant is lower than the voltage drop threshold value and the SVG reaches the upper limit of reactive power, determining the reactive power output weight of each wind turbine generator through each adjustment sensitivity, and starting the wind turbine generator according to the reactive power output weight and the current reactive power demand to carry out secondary reactive power support. According to the invention, the problems of insufficient coordination among equipment, slow dynamic response speed and easy generation of reactive oscillation in the reactive voltage control of the existing wind power plant can be solved.

Description

Technical Field

[0001] This invention relates to the field of renewable energy grid connection and reactive voltage coordinated control technology, and in particular to a method, device and equipment for graded control of reactive voltage in wind farm SVG. Background Technology

[0002] With the large-scale grid connection of wind power, the problems of uneven voltage distribution and reactive power compensation within wind farms are becoming increasingly prominent. Traditional wind farm voltage control mainly relies on static reactive power compensation devices, such as capacitor banks, but their response speed is slow and they are difficult to adapt to dynamic changes in the power grid. When a voltage dip occurs in the grid, the wind farm is prone to voltage instability, leading to wind turbine disconnection and affecting system safety. Existing methods mostly employ hierarchical control, but the coordination between equipment is somewhat insufficient, resulting in problems such as reactive power oscillation and response lag.

[0003] A wind farm SVG (Static Var Generator) is an SVG installed in the substation of a wind farm. It uses fully controlled power electronic devices (IGBTs) to absorb or generate reactive power in real time, stabilizing the voltage at the grid connection point within the range required by the grid, and solving problems such as voltage fluctuations and low power factor caused by large-scale wind turbine grid connection.

[0004] Currently, scholars have proposed various reactive power and voltage control strategies to improve the grid connection stability of wind farms, but these strategies still have significant shortcomings. Firstly, the mainstream reactive power and voltage control strategies include constant reactive power control and constant AC voltage control. Constant reactive power control sets a fixed reactive power output value, such as SVG maintaining constant reactive power injection, but it cannot adapt to grid voltage fluctuations. Constant AC voltage control aims to maintain stable PCC (grid connection point) voltage, such as dynamically adjusting reactive power output through a PI regulator, but its response speed is greatly affected by parameter tuning. In addition, there is local voltage measurement-based control, such as wind turbines adjusting reactive power according to their own terminal voltage, but this lacks coordination between units. These strategies often operate independently; when SVG and wind turbines use different control modes, it leads to asynchronous operation between equipment, and even reactive power oscillations during faults. Summary of the Invention

[0005] This invention provides a method, apparatus, and equipment for graded control of reactive voltage in wind farm SVG, in order to solve the problems of insufficient coordination between equipment, slow dynamic response speed, and easy reactive voltage oscillation in existing wind farm reactive voltage control.

[0006] In a first aspect, embodiments of the present invention provide a reactive power and voltage graded control method suitable for wind farm SVG, comprising: Based on the equivalent circuit model of the wind farm collection network, the fitting equation of reactive power demand and grid voltage is obtained, as well as the adjustment sensitivity of each equivalent wind farm to the grid connection point voltage of the wind farm in the equivalent circuit model. The real-time grid connection point voltage of the wind farm is obtained. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is started to provide first-level reactive power support according to the current reactive power demand. When the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power, the reactive power output weight of each wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the wind farm grid connection point voltage. Based on the reactive power output weight and the current reactive power demand, the wind turbine is started to provide secondary reactive power support.

[0007] In one possible implementation, the equivalent circuit model based on the wind farm collector network obtains the fitting equation of reactive power demand and grid voltage, as well as the adjustment sensitivity of each equivalent wind farm in the equivalent circuit model to the voltage at the wind farm grid connection point, including: Construct an equivalent circuit model of the wind farm's power collection network to obtain the power balance equation at the wind farm's grid connection point; Based on the power balance equation at the grid connection point of the wind farm, the fitting equation between reactive power demand and grid voltage is obtained through continuous power flow calculation and curve fitting. The sensitivity of each equivalent wind field to the voltage regulation at the grid connection point of the wind farm is obtained based on the admittance matrix of the collector network nodes.

[0008] In one possible implementation, the step of constructing an equivalent circuit model of the wind farm's power collection network to obtain the power balance equation at the wind farm's grid connection point includes: The equivalent circuit model of the wind farm's power collection network includes a grid-connected main line, an SVG, and... N One equivalent wind field; the grid-connected main line is connected to N The system includes one feeder line and one wind farm transmission line, with each feeder line connected to one of the equivalent wind farms; the SVG is connected to the grid main line. The power balance equation at the grid connection point of the wind farm is as follows: ; Line impedance per unit length: Z 0 = R 0 + jX 0; No. k Impedance of the feeder: Z k = L kR 0 + jL k X 0; Impedance value of wind farm transmission lines: Z w = R w + jX w ; in, k =1, 2, ..., N , N The number of equivalent wind fields. L k For the first k Line length, R 0 represents unit resistance. X 0 represents unit reactance. R w The resistance of the wind farm's power transmission line. X w For the reactor of the wind farm's transmission line, U k For the first k The voltage at the wind farm node on the feeder line, where V0 is the grid voltage. This refers to the voltage at the wind farm's grid connection point. This is for reactive power demand.

[0009] In one possible implementation, obtaining the fitting equation between reactive power demand and grid voltage based on the power balance equation at the wind farm grid connection point through continuous power flow calculation and curve fitting includes: Set a step size so that the grid voltage decreases from a first voltage to a second voltage according to the step size, simulating a grid voltage drop, wherein the first voltage is greater than a voltage drop threshold and the second voltage is less than a voltage drop threshold; During the simulation of grid voltage drop, when the voltage at the wind farm grid connection point is higher than the voltage drop threshold, the wind farm grid connection point is set as a reactive power fixed PQ node, and the reactive power support is set to 0. The voltage at the wind farm grid connection point is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. In the process of simulating grid voltage drop, when the voltage at the wind farm grid connection point is lower than the voltage drop threshold, the wind farm grid connection point is set as a fixed voltage PV node, and the voltage at the wind farm grid connection point is set to be equal to the voltage drop threshold. The reactive power demand is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. Record key electrical quantities during the simulated grid voltage drop process, including grid voltage, wind farm grid connection point voltage, reactive power demand, and wind farm grid connection point type, and then proceed to the next iteration; After the iteration is completed, the reactive power demand is plotted as a function of grid voltage based on the key electrical quantities. The curve is then fitted with a quadratic polynomial to obtain the fitting equation between reactive power demand and grid voltage.

[0010] In one possible implementation, the sensitivity of each equivalent wind field to the voltage regulation at the wind farm grid connection point is obtained based on the admittance matrix of the wind farm collector network, including: according to , obtained the k The sensitivity of equivalent wind field to the voltage regulation at the grid connection point of wind farm; in, For the first k The reactive power support provided by an equivalent wind field The node admittance matrix of the wind farm collection network is obtained by inverting the node admittance matrix, which is calculated offline based on the wind farm line impedance and wind farm node voltage.

[0011] In one possible implementation, when the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG has not reached its reactive power limit, the current reactive power demand is determined based on the real-time wind farm grid connection point voltage and the fitted equation, and the SVG is activated for primary reactive power support based on the current reactive power demand, including: Calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation; If the voltage deviation at the wind farm's grid connection point is greater than the first deviation threshold, the reactive power demand is determined based on the real-time wind farm grid connection point voltage and the fitted equation, and the SVG is activated to provide primary reactive power support based on the current reactive power demand. When the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the reactive power limit, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the wind farm grid connection point voltage. Based on the reactive power output weight and the current reactive power demand, the wind turbines are activated for secondary reactive power support, including: Calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation; If the voltage deviation at the grid connection point of the wind farm is greater than the second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm. Based on the reactive power output weight and the current reactive power demand, the wind turbine is started to provide secondary reactive power support.

[0012] In one possible implementation, if the voltage deviation at the wind farm's grid connection point is greater than a second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined based on the adjustment sensitivity of each equivalent wind farm to the wind farm's grid connection point voltage. Then, based on the reactive power output weight and the current reactive power demand, the wind turbines are activated for secondary reactive power support, including: The reactive power correction amount is determined based on the voltage deviation at the grid connection point of the wind farm. The reactive power output weight of each equivalent wind turbine is determined by the sensitivity of each equivalent wind field to the voltage at the grid connection point of the wind farm. The current reactive power demand and the reactive power correction amount are allocated according to the reactive power output weight, and the wind turbine is started to provide secondary reactive power support according to the allocation result.

[0013] In one possible implementation, the current reactive power demand and the reactive power correction amount are allocated according to the reactive power output weight, and the wind turbine generators are activated for secondary reactive power support according to the allocation result, including: according to Start the wind turbine for secondary reactive power support; in, To start the k The reactive power support that the wind turbines corresponding to the equivalent wind farm should provide. For the current reactive power demand, This is the reactive power correction amount. For the first k The reactive power output weight of wind turbines corresponding to equivalent wind farms N The number of equivalent wind fields. For the first k Sensitivity of equivalent wind field to the voltage regulation at the grid connection point of wind farm.

[0014] Secondly, embodiments of the present invention provide a reactive power and voltage graded control device suitable for wind farm SVG, comprising: The equivalent circuit model solving module is used to obtain the fitting equation of reactive power demand and grid voltage based on the equivalent circuit model of the wind farm collection network, as well as the adjustment sensitivity of each equivalent wind farm to the voltage at the wind farm grid connection point in the equivalent circuit model. The primary reactive power support module is used to obtain the real-time grid connection point voltage of the wind farm. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is activated to provide primary reactive power support according to the current reactive power demand. The secondary reactive power support module is used to determine the reactive power output weight of each equivalent wind turbine unit by means of the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm when the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power. Based on the reactive power output weight and the current reactive power demand, the wind turbine unit is started to provide secondary reactive power support.

[0015] Thirdly, embodiments of the present invention provide a reactive voltage graded control device suitable for wind farm SVG, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the method in the first aspect or any possible implementation of the first aspect.

[0016] In this embodiment of the invention, without increasing the capacity of the reactive power compensation device, the reactive power regulation potential of the Static Var Generator (SVG) and Wind Turbine Generators (WTGs) within the wind farm is fully explored and coordinated. Specifically, by obtaining the fitting equation of reactive power demand and grid voltage, and the regulation sensitivity of each equivalent wind farm to the grid connection point voltage of the wind farm, when the grid voltage drops, the SVG prioritizes determining the current reactive power demand based on the fitting equation and provides primary support. When the SVG reaches the upper limit of reactive power but the voltage deviation at the wind farm grid connection point still exceeds the limit, the current reactive power demand is optimized and allocated based on each regulation sensitivity to achieve secondary support. This enables the rapid recovery of the wind farm grid connection point voltage and the stable distribution of internal voltage, effectively improving the grid connection stability of the wind farm and its voltage support capability to the grid. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the implementation of the reactive power and voltage hierarchical control method for wind farm SVG provided in this embodiment of the invention. Figure 2 This is a schematic diagram of the equivalent circuit model of the wind farm power collection network provided in an embodiment of the present invention; Figure 3 This is a flowchart illustrating the implementation of the fitting equation for obtaining reactive power demand and grid voltage, provided in an embodiment of the present invention. Figure 4 The grid connection point voltage in this embodiment of the invention V PCC With grid voltage V 0 change relationship curve; Figure 5 This is the reactive power requirement in the embodiments of the present invention. With grid voltage V 0 as a function of time; Figure 6 In this embodiment of the invention, the node type varies with the grid voltage. V A diagram illustrating the case where 0 changes. Figure 7This is a flowchart of the graded control method for reactive voltage graded regulation in this embodiment of the invention; Figure 8 This is a schematic diagram of the curves showing the effective value of the grid connection point voltage and the effective value of the line voltage of the first equivalent wind farm changing over time in Comparative Example 1 of the present invention. Figure 9 This is a schematic diagram of the active power curves of the wind farm transmission line and the first equivalent wind farm in Comparative Example 1 of the present invention. Figure 10 This is a schematic diagram of the reactive power timing curves of each line in Comparative Example 1 of the present invention; Figure 11 This is a schematic diagram of the curves showing the changes in the effective value of the grid connection point voltage and the effective value of the line voltage of the first equivalent wind farm over time in Embodiment 1 of the present invention. Figure 12 This is a schematic diagram of the active power curves of the wind farm transmission line and the first equivalent wind farm in Embodiment 1 of the present invention; Figure 13 This is a schematic diagram of the reactive power timing curves of each line in Embodiment 1 of the present invention; Figure 14 This is a reactive voltage graded control device applicable to wind farm SVG in the embodiments of the present invention; Figure 15 This is a reactive voltage graded control device applicable to wind farm SVG in the embodiments of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] Figure 1 The implementation flowchart of the reactive power and voltage hierarchical control method for wind farm SVG provided in this embodiment of the invention is described in detail below: In step 101, based on the equivalent circuit model of the wind farm collection network, the fitting equation of reactive power demand and grid voltage is obtained, as well as the adjustment sensitivity of each equivalent wind farm to the grid connection point voltage of the wind farm in the equivalent circuit model.

[0020] In step 102, the real-time grid connection point voltage of the wind farm is obtained. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is started to provide first-level reactive power support according to the current reactive power demand.

[0021] In step 103, when the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power, the reactive power output weight of each wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the wind farm grid connection point voltage, and the wind turbine is started to provide secondary reactive power support according to the reactive power output weight and the current reactive power demand.

[0022] In one embodiment, step 101 includes: Construct an equivalent circuit model of the wind farm's power collection network to obtain the power balance equation at the wind farm's grid connection point.

[0023] Figure 2 This is a schematic diagram of the equivalent circuit model of the wind farm power collection network provided in an embodiment of the present invention.

[0024] For example, such as Figure 2 As shown, there are two connecting feeders in the wind farm, each feeder connecting to an equivalent wind farm. Let the first equivalent wind farm be the first node 201, the second equivalent wind farm be the second node 202, and the grid connection point be the third node 203.

[0025] The impedance per unit length of the line is: Z 0 = R 0 + jX 0(1) The length of the first feeder is L 1. The line impedance value Z1 is: Z 1 = R 1 + jX 1= L 1 Z 0= L 1 R 0 + jL 1 X 0(2) The length of the second feeder is L 2. The line impedance value Z2 is: Z 2 = R 2 + jX 2= L 2 Z 0= L 2 R 0 + jL 2 X 0(3) Impedance value of wind farm transmission lines Z W for: Z w = R w + jX w (4) The power balance at the first node 201 is: (5) The power balance equation for the second node 202 is: (6) The power balance equation for the third node 203 is: (7) Based on the power balance equation at the grid connection point of the wind farm, the fitting equation between reactive power support and grid voltage is obtained through continuous power flow calculation and curve fitting.

[0026] This invention constructs an equivalent circuit model of the wind farm's power collection network and obtains the power balance equation at the wind farm's grid connection point. This provides a precise mathematical model foundation for quantitative analysis of voltage distribution characteristics and subsequent coordinated control methods.

[0027] Figure 3 The following is a flowchart illustrating the implementation of the fitting equation for obtaining reactive power demand and grid voltage, provided by an embodiment of the present invention: Set a step size so that the grid voltage decreases from a first voltage to a second voltage in steps to simulate a grid voltage drop. The first voltage is greater than the voltage drop threshold, and the second voltage is less than the voltage drop threshold.

[0028] For example, the specific power flow calculation settings are as follows: voltage sag threshold is set to 0.9 pu, first voltage is set to 1.0 pu, second voltage is set to 0.8 pu, step size is set to -0.002 pu, and grid voltage... V The voltage drops are simulated by decreasing from 1.0 pu in steps of -0.002 pu to 0.8 pu.

[0029] During the simulation of grid voltage drop, when the voltage at the wind farm grid connection point is higher than the voltage drop threshold, the wind farm grid connection point is set as a reactive power fixed PQ node, and the reactive power support is set to 0. The voltage at the wind farm grid connection point is obtained by solving N+1 sets of power balance equations for the wind farm grid connection point.

[0030] For example, when V PCC When >0.9 pu, set =0; at this time U 1, U 2, V PCC All are unknowns. By solving the three third-node power balance equations, we obtain... U 1, U 2, V PCC .

[0031] In the process of simulating grid voltage drop, when the voltage at the wind farm grid connection point is lower than the voltage drop threshold, the wind farm grid connection point is set as a fixed voltage PV node, and the voltage at the wind farm grid connection point is set to be equal to the voltage drop threshold. The reactive power demand is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point.

[0032] For example, when V PCC When ≤0.9pu, set V PCC =0.9pu; at this time U 1, U 2, All are unknowns. By solving the three third-node power balance equations, we obtain... U 1, U 2, .

[0033] For each V PCC The value, the determination of the system's operating mode, depends on the value obtained from the previous iteration. V PCC The value is calculated by switching the wind farm grid connection point to the corresponding node.

[0034] Record key electrical quantities during the simulated grid voltage drop process, including grid voltage, wind farm grid connection point voltage, reactive power demand, and wind farm grid connection point type, and then proceed to the next iteration.

[0035] After the iteration is completed, the curve of reactive power demand changing with grid voltage is plotted based on key electrical quantities. The curve is then fitted with a quadratic polynomial to obtain the fitting equation of reactive power demand and grid voltage.

[0036] This invention proposes an adaptive switching mechanism for point-of-connection (PCC) node types based on a voltage drop threshold. When the PCC voltage is higher than the voltage drop threshold (e.g., 0.9 pu), it is treated as a PQ node; when the voltage is lower than the threshold, it switches to a PV node, and the voltage is maintained by calculating the required reactive power, thus achieving a smooth transition of control modes.

[0037] For example, after obtaining the simulation data, the grid connection point voltage is plotted. V PCC With grid voltage V 0 change relationship curve, such as Figure 4 As shown.

[0038] For example, after obtaining the simulation data, the reactive power demand is plotted. With grid voltage V The curve showing the relationship between 0 and its variation, such as Figure 5 As shown.

[0039] For example, by fitting the curve with a quadratic polynomial, the fitting equation for reactive power demand and grid voltage is obtained: =-6.005V 0 +1285.13 (8) This invention quantifies the relationship between system reactive power demand and grid voltage sag through continuous power flow calculation and curve fitting. A fitting equation for reactive power demand and grid voltage is derived, providing a basis for reactive power tuning.

[0040] Node type varies with grid voltage V The case of 0 change is as follows Figure 6 As shown.

[0041] Depend on Figure 4 , 5 As can be seen from 6, when the grid voltage V When the voltage drops from 1.0 pu, the grid connection point voltage V PCC It also drops along with the voltage. At this point, the SVG does not generate reactive power, and the grid connection point is the PQ node, until the grid connection point voltage drops. V PCC When the power consumption drops below 0.9 PU, it begins to generate reactive power, and the grid connection point changes from a PQ node to a PV node.

[0042] The sensitivity of each equivalent wind field to the voltage regulation at the wind farm grid connection point is obtained based on the admittance matrix of the collector network nodes. Sensitivity of the first equivalent wind field to PCC voltage S 1 is: (9) Sensitivity of the second equivalent wind field to PCC voltage S 2 is: (10) in, Reactive power support provided for the first-order wind field. Reactive power support provided for the second equivalent wind field , It is obtained by inverting the node admittance matrix of the wind farm collector network. The node admittance matrix is ​​obtained by offline calculation based on the wind farm line impedance and wind farm node voltage.

[0043] Reactive power distribution among wind turbine units follows a sensitivity-priority principle, meaning that units with high grid connection voltage regulation sensitivity generate more reactive power, while units with low sensitivity generate less, thus achieving coordinated optimization and ensuring that the voltage recovers to within the allowable range. This reactive power and voltage tiered control method, applicable to wind farm SVG, is based on the comprehensive utilization of the characteristics of different reactive power sources.

[0044] This invention uses "reactive power-voltage sensitivity" as the criterion for reactive power allocation among wind turbine units. Reactive power increments are allocated based on each wind farm's ability (sensitivity) to regulate the voltage at its point of connection (PCC). Units with higher sensitivity generate more reactive power, achieving an economically optimized allocation of reactive resources within the wind farm and aiming to reduce network losses.

[0045] In one embodiment, step 102 includes: Calculate the difference between the real-time grid connection voltage of the wind farm and the voltage drop threshold to obtain the grid connection voltage deviation of the wind farm.

[0046] For example, calculate the voltage deviation at the grid connection point of the wind farm: (11) in, This is the reference value for the grid connection point voltage, and here it is taken as the voltage drop threshold.

[0047] If the voltage deviation at the wind farm's grid connection point exceeds the first deviation threshold, the reactive power demand is determined based on the real-time wind farm grid connection point voltage and the fitted equation, and the SVG is activated to provide primary reactive power support based on the reactive power demand.

[0048] For example, the first deviation threshold ΔU 1 represents 0.02 pu.

[0049] In one embodiment, step 103 includes: Calculate the difference between the real-time grid connection voltage of the wind farm and the voltage drop threshold to obtain the grid connection voltage deviation of the wind farm.

[0050] For example, calculate the voltage deviation at the grid connection point of the wind farm: (12) in, This is the reference value for the grid connection point voltage, and here it is taken as the voltage drop threshold.

[0051] If the voltage deviation at the grid connection point of the wind farm is greater than the second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm. Based on the reactive power output weight and reactive power demand, the wind turbine is started to provide secondary reactive power support.

[0052] For example, the second deviation threshold ΔU 2 is 0.05 pu.

[0053] This invention clarifies the action threshold (dead zone) for hierarchical control. Two key voltage deviation thresholds are set ( ΔU1 and ΔU2 These are used to trigger the SVG to provide primary reactive power support and the wind turbine to provide secondary reactive power support, respectively, thus avoiding frequent equipment operation and reactive power oscillation.

[0054] The reactive power correction amount is determined based on the voltage deviation at the grid connection point of the wind farm.

[0055] In one embodiment, a closed-loop mechanism for the voltage deviation at the wind farm's grid connection point is introduced into the secondary reactive power support provided by the wind turbine based on the current reactive power demand, thereby controlling the voltage deviation at the wind farm's grid connection point. ΔV This is converted into reactive power correction through a proportional element: (13) in, This is a correction factor.

[0056] By introducing a closed-loop compensation system for reactive power commands based on voltage deviation feedback, the reactive power output commands are dynamically corrected, thereby achieving rapid recovery of the voltage at the wind farm's grid connection point and stable distribution of the internal voltage, effectively improving the grid connection stability of the wind farm and its voltage support capability for the power grid.

[0057] The reactive power output weight of each equivalent wind turbine is determined by the sensitivity of each equivalent wind farm to the voltage at the wind farm's grid connection point. Based on the reactive power output weight, the current reactive power demand and reactive power correction are allocated, and the wind turbines are activated for secondary reactive power support according to the allocation results.

[0058] It should be noted that since this embodiment is executed after the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the reactive power limit, the real-time grid voltage at this time is the real-time grid voltage obtained under the condition that the SVG provides the reactive power limit. Therefore, it is only necessary to allocate the current reactive demand and reactive power correction amount corresponding to the real-time grid voltage at this time according to the reactive power output weight.

[0059] For example, the reactive power correction is added to the current reactive power demand. The reactive power support provided by the wind turbines corresponding to the first equivalent wind field and the reactive power support provided by the wind turbines corresponding to the second equivalent wind field are allocated according to the adjustment sensitivity.

[0060] The reactive power support provided by the wind turbines corresponding to the first-equivalent wind farm is: (14) The reactive power support provided by the wind turbines corresponding to the second equivalent wind farm is: (15) Figure 7 This is a flowchart of the graded control method for reactive power and voltage graded regulation of the present invention; the above process is as follows: Figure 7 As shown.

[0061] To further illustrate the reactive power and voltage graded control method applicable to wind farm SVG provided in the embodiments of the present invention, a system is built in PSCAD / EMTDC electromagnetic simulation software as follows: Figure 2 The equivalent circuit model of the wind farm collector network is shown.

[0062] Comparative Example 1 A simulation of a grid voltage drop was conducted. The control strategy involved both the SVG and the wind turbine using a constant AC voltage control mode. At t=2s, the grid voltage suddenly dropped from 230kV to 172.5kV, and recovered after 0.5s. The simulation results are as follows. Figure 8 , Figure 9 , Figure 10 As shown.

[0063] Example 1 The simulation tested a grid voltage drop scenario. The control strategy employed constant reactive power control for both the SVG (Static Var Generator) and the wind turbine, along with a coordinated control strategy between the SVG and the wind farm. A reactive power feedback closed loop was also added to the wind turbine layer. At t=2s, the grid voltage dropped sharply from 230kV to 172.5kV, and recovered after 0.5s. The simulation results are as follows: Figure 11 , Figure 12 , Figure 13 As shown.

[0064] Figure 8 — Figure 13 The parameters are explained as follows: VLINE_RMS is the effective voltage value of the PCC at the grid connection point, and VWIND1_RMS is the effective voltage value of the feeder voltage at the first equivalent wind farm. P_LINE is the active power of the wind farm's transmission line, and P_WIND1 is the active power of the feeder at the first equivalent wind farm. Q_LINE is the reactive power of the wind farm's transmission line, Q_ST is the reactive power of the line where the SVG is located, Q_WIND1 is the reactive power of the feeder at the first equivalent wind farm, and Q_WIND2 is the reactive power of the feeder at the second equivalent wind farm.

[0065] Depend on Figure 8 — Figure 13 It can be seen that during the entire voltage drop process, the reactive power and voltage tiered control method applicable to the wind farm SVG can reduce the fluctuation of reactive power curves of each line and make the response process smoother. This indicates that coordinated control avoids disordered responses between equipment and makes reactive power distribution more orderly. Moreover, the voltage recovery speed and final stable value after fault clearance are both better, which simulation verifies the effectiveness of the coordinated control strategy in improving voltage support capability.

[0066] The effectiveness of the reactive power and voltage hierarchical control method applicable to wind farm SVG was verified using electromagnetic transient simulation (PSCAD / EMTDC). Simulation results show that this strategy enables more orderly reactive power distribution, a smoother response process, and faster and more stable voltage recovery after fault clearance, demonstrating its engineering application value.

[0067] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0068] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0069] Figure 14 A schematic diagram of the structure of the reactive power and voltage graded control device for wind farm SVG provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 14 As shown, the reactive power and voltage graded control device 14 suitable for wind farm SVG includes: The equivalent circuit model solving module 1401 is used to obtain the fitting equation of reactive power demand and grid voltage based on the equivalent circuit model of the wind farm collection network, as well as the adjustment sensitivity of each equivalent wind farm to the voltage at the wind farm grid connection point in the equivalent circuit model.

[0070] The primary reactive power support module 1402 is used to obtain the real-time grid connection point voltage of the wind farm. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is activated to provide primary reactive power support according to the current reactive power demand.

[0071] The secondary reactive power support module 1403 is used to determine the reactive power output weight of each wind turbine unit by the adjustment sensitivity of each equivalent wind farm to the voltage at the wind farm's grid connection point when the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power. Based on the reactive power output weight and the current reactive power demand, the wind turbine units are started to provide secondary reactive power support.

[0072] In one possible implementation, the equivalent circuit model solving module 1401 can be used to construct the equivalent circuit model of the wind farm collection network and obtain the power balance equation at the wind farm grid connection point. Based on the power balance equation at the wind farm grid connection point, the fitting equation between reactive power demand and grid voltage is obtained through continuous power flow calculation and curve fitting. The sensitivity of each equivalent wind field to the voltage regulation at the grid connection point of the wind farm is obtained based on the admittance matrix of the collector network nodes.

[0073] In one possible implementation, the equivalent circuit model of the wind farm collector network constructed by the equivalent circuit model solving module 1401 includes a grid-connected main line, an SVG, and... N One equivalent wind field; grid connection main line NOne feeder and one wind farm transmission line, each feeder connected to an equivalent wind farm; the SVG is connected to the grid main line; The power balance equation at the grid connection point of the wind farm is: ; Line impedance per unit length: Z 0 = R 0 + jX 0; No. k Impedance of the feeder: Z k = L k R 0 + jL k X 0; Impedance value of wind farm transmission lines: Z w = R w + jX w ; in, k =1, 2, ..., N , N The number of equivalent wind fields. L k For the first k Line length, R 0 represents unit resistance. X 0 represents unit reactance. R w The resistance of the wind farm's power transmission line. X w For the reactor of the wind farm's transmission line, U k For the first k The voltage at the wind farm node on the feeder line, where V0 is the grid voltage. This refers to the voltage at the wind farm's grid connection point. This is for reactive power demand.

[0074] In one possible implementation, the equivalent circuit model solving module 1401 can be used to set a step size so that the grid voltage decreases from a first voltage to a second voltage in steps to simulate a grid voltage drop, wherein the first voltage is greater than a voltage drop threshold and the second voltage is less than a voltage drop threshold. During the simulation of grid voltage drop, when the voltage at the wind farm grid connection point is higher than the voltage drop threshold, the wind farm grid connection point is set as a reactive power fixed PQ node, and the reactive power support is set to 0. The voltage at the wind farm grid connection point is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. In the process of simulating grid voltage drop, when the voltage at the wind farm grid connection point is lower than the voltage drop threshold, the wind farm grid connection point is set as a fixed voltage PV node, and the voltage at the wind farm grid connection point is set to be equal to the voltage drop threshold. The reactive power demand is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. Record key electrical quantities during the simulated grid voltage drop process, including grid voltage, wind farm grid connection point voltage, reactive power demand, and wind farm grid connection point type, and then proceed to the next iteration; After the iteration is completed, the curve of reactive power demand changing with grid voltage is plotted based on key electrical quantities. The curve is then fitted with a quadratic polynomial to obtain the fitting equation of reactive power demand and grid voltage.

[0075] In one possible implementation, the equivalent circuit model solving module 1401 can be used to solve the circuit model based on... , obtained the k The sensitivity of equivalent wind field to the voltage regulation at the grid connection point of wind farm; in, For the first k The reactive power support provided by an equivalent wind field The node admittance matrix of the wind farm collector network is obtained by inverting the node admittance matrix, which is calculated offline based on the wind farm line impedance and wind farm node voltage.

[0076] In one possible implementation, the primary reactive power support module 1402 can be used to calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation. If the voltage deviation at the wind farm's grid connection point exceeds the first deviation threshold, the reactive power demand is determined based on the real-time voltage at the wind farm's grid connection point and the fitted equation, and the SVG is activated to provide primary reactive power support based on the current reactive power demand.

[0077] In one possible implementation, the secondary reactive power support module 1403 can be used to calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation. If the voltage deviation at the grid connection point of the wind farm is greater than the second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm. Based on the reactive power output weight and the current reactive power demand, the wind turbine is started to provide secondary reactive power support.

[0078] In one possible implementation, the secondary reactive power support module 1403 can be used to determine the reactive power correction amount based on the voltage deviation at the wind farm grid connection point. The reactive power output weight of each equivalent wind turbine is determined by the sensitivity of each equivalent wind field to the voltage at the grid connection point of the wind farm. The current reactive power demand and reactive power correction are allocated according to the reactive power output weight, and the wind turbine units are started to provide secondary reactive power support according to the allocation results.

[0079] In one possible implementation, the secondary reactive power support module 1403 can be used to... Start the wind turbine for secondary reactive power support; in, To start the k The reactive power support that the wind turbines corresponding to the equivalent wind farm should provide. For current reactive power demand, This is the reactive power correction amount. For the first k The reactive power output weight of wind turbines corresponding to equivalent wind farms N The number of equivalent wind fields. For the first k Sensitivity of equivalent wind field to the voltage regulation at the grid connection point of wind farm.

[0080] Figure 15 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 15 As shown, the electronic device 15 of this embodiment includes a processor 1500 and a memory 1501. The memory 1501 stores a computer program 1502. When the processor 1500 executes the computer program 1502, it implements the steps in the various method embodiments described above. Alternatively, when the processor 1500 executes the computer program 1502, it implements the functions of each module / unit in the various device embodiments described above.

[0081] For example, computer program 1502 may be divided into one or more modules / units, which are stored in memory 1501 and executed by processor 1500 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 1502 in electronic device 15.

[0082] Electronic device 15 may include, but is not limited to, processor 1500 and memory 1501. Those skilled in the art will understand that... Figure 15 This is merely an example of electronic device 15 and does not constitute a limitation on electronic device 15. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device 15 may also include input / output devices, network access devices, buses, etc.

[0083] For the sake of simplicity and clarity, only the above-described functional modules / units are used as examples. In practical applications, the functions described above can be assigned to different functional modules / units as needed. These modules / units can be implemented in hardware, software, or a combination of both.

[0084] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not detailed or described in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Unless otherwise specified or in conflict with logic, the terminology and / or descriptions between different embodiments are consistent and can be referenced interchangeably. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for graded control of reactive power and voltage suitable for wind farm SVG, characterized in that, include: Based on the equivalent circuit model of the wind farm collection network, the fitting equation of reactive power demand and grid voltage is obtained, as well as the adjustment sensitivity of each equivalent wind farm to the grid connection point voltage of the wind farm in the equivalent circuit model. The real-time grid connection point voltage of the wind farm is obtained. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is started to provide first-level reactive power support according to the current reactive power demand. When the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power, the reactive power output weight of each wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the wind farm grid connection point voltage. Based on the reactive power output weight and the current reactive power demand, the wind turbine is started to provide secondary reactive power support.

2. The reactive power and voltage hierarchical control method applicable to wind farm SVG according to claim 1, characterized in that, The equivalent circuit model based on the wind farm collector network obtains the fitting equation of reactive power demand and grid voltage, as well as the adjustment sensitivity of each equivalent wind farm to the grid connection point voltage in the equivalent circuit model, including: Construct an equivalent circuit model of the wind farm's power collection network to obtain the power balance equation at the wind farm's grid connection point; Based on the power balance equation at the grid connection point of the wind farm, the fitting equation between reactive power demand and grid voltage is obtained through continuous power flow calculation and curve fitting. The sensitivity of each equivalent wind field to the voltage regulation at the grid connection point of the wind farm is obtained based on the admittance matrix of the collector network nodes.

3. The reactive power and voltage hierarchical control method applicable to wind farm SVG according to claim 2, characterized in that, The equivalent circuit model of the wind farm's power collection network is constructed to obtain the power balance equation at the wind farm's grid connection point, including: The equivalent circuit model of the wind farm's power collection network includes a grid-connected main line, an SVG, and... N One equivalent wind field; the grid-connected main line is connected to N The system includes one feeder line and one wind farm transmission line, with each feeder line connected to one of the equivalent wind farms; the SVG is connected to the grid main line. The power balance equation at the grid connection point of the wind farm is as follows: ； Line impedance per unit length: Z 0 = R 0 + jX 0； No. k Impedance of the feeder: Z k = L k R 0 + jL k X 0； Impedance value of wind farm transmission lines: Z w = R w + jX w ； in, k =1, 2, ..., N , N The number of equivalent wind fields, L k For the first k Line length, R 0 represents unit resistance. X 0 represents unit reactance. R w The resistance of the wind farm's power transmission line. X w For the reactor of the wind farm's transmission line, U k For the first k The voltage at the wind farm node on the feeder line, where V0 is the grid voltage. This refers to the voltage at the wind farm's grid connection point. This is for reactive power demand.

4. The reactive power and voltage hierarchical control method for wind farm SVG according to claim 3, characterized in that, The process involves obtaining a fitting equation between reactive power demand and grid voltage based on the power balance equation at the wind farm's grid connection point, through continuous power flow calculations and curve fitting. This includes: Set a step size so that the grid voltage decreases from a first voltage to a second voltage according to the step size, simulating a grid voltage drop, wherein the first voltage is greater than a voltage drop threshold and the second voltage is less than a voltage drop threshold; During the simulation of grid voltage drop, when the voltage at the wind farm grid connection point is higher than the voltage drop threshold, the wind farm grid connection point is set as a reactive power fixed PQ node, and the reactive power support is set to 0. The voltage at the wind farm grid connection point is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. In the process of simulating grid voltage drop, when the voltage at the wind farm grid connection point is lower than the voltage drop threshold, the wind farm grid connection point is set as a fixed voltage PV node, and the voltage at the wind farm grid connection point is set to be equal to the voltage drop threshold. The reactive power demand is obtained by solving N+1 sets of power balance equations at the wind farm grid connection point. Record key electrical quantities during the simulated grid voltage drop process, including grid voltage, wind farm grid connection point voltage, reactive power demand, and wind farm grid connection point type, and then proceed to the next iteration; After the iteration is completed, the reactive power demand is plotted as a function of grid voltage based on the key electrical quantities. The curve is then fitted with a quadratic polynomial to obtain the fitting equation between reactive power demand and grid voltage.

5. The reactive power and voltage hierarchical control method applicable to wind farm SVG according to claim 2, characterized in that, The sensitivity of each equivalent wind farm to the voltage regulation at the wind farm grid connection point is obtained based on the admittance matrix of the wind farm collector network, including: according to , obtained the k The sensitivity of equivalent wind field to the voltage regulation at the grid connection point of wind farm; in, For the first k The reactive power support provided by an equivalent wind field The node admittance matrix of the wind farm collection network is obtained by inverting the node admittance matrix, which is calculated offline based on the wind farm line impedance and the wind farm node voltage.

6. The reactive power and voltage hierarchical control method applicable to wind farm SVG according to claim 1, characterized in that, When the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG has not reached the reactive power limit, the current reactive power demand is determined based on the real-time wind farm grid connection point voltage and the fitted equation, and the SVG is activated for primary reactive power support based on the current reactive power demand, including: Calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation; If the voltage deviation at the wind farm's grid connection point is greater than the first deviation threshold, the reactive power demand is determined based on the real-time wind farm grid connection point voltage and the fitted equation, and the SVG is activated to provide primary reactive power support based on the current reactive power demand. When the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the reactive power limit, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the wind farm grid connection point voltage. Based on the reactive power output weight and the current reactive power demand, the wind turbines are activated for secondary reactive power support, including: Calculate the difference between the real-time wind farm grid connection point voltage and the voltage drop threshold to obtain the wind farm grid connection point voltage deviation; If the voltage deviation at the grid connection point of the wind farm is greater than the second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm. Based on the reactive power output weight and the current reactive power demand, the wind turbine is started to provide secondary reactive power support.

7. The reactive power and voltage graded control method applicable to wind farm SVG according to claim 6, characterized in that, If the voltage deviation at the grid connection point of the wind farm is greater than the second deviation threshold, the reactive power output weight of each equivalent wind turbine is determined by the adjustment sensitivity of each equivalent wind farm to the grid connection point voltage. Based on the reactive power output weight and the current reactive power demand, the wind turbines are started to provide secondary reactive power support, including: The reactive power correction amount is determined based on the voltage deviation at the grid connection point of the wind farm. The reactive power output weight of each equivalent wind turbine is determined by the sensitivity of each equivalent wind field to the voltage at the grid connection point of the wind farm. The current reactive power demand and the reactive power correction amount are allocated according to the reactive power output weight, and the wind turbine is started to provide secondary reactive power support according to the allocation result.

8. The reactive power and voltage hierarchical control method for wind farm SVG according to claim 7, characterized in that, The current reactive power demand and the reactive power correction amount are allocated according to the reactive power output weight, and the wind turbine units are started for secondary reactive power support according to the allocation result, including: according to Start the wind turbine for secondary reactive power support; in, To start the k The reactive power support that the wind turbines corresponding to the equivalent wind farm should provide. For the current reactive power demand, This is the reactive power correction amount. For the first k The reactive power output weight of wind turbines corresponding to equivalent wind farms N The number of equivalent wind fields, For the first k Sensitivity of equivalent wind field to the voltage regulation at the grid connection point of the wind farm.

9. A reactive power and voltage graded control device suitable for wind farm SVG, characterized in that, include: The equivalent circuit model solving module is used to obtain the fitting equation of reactive power demand and grid voltage based on the equivalent circuit model of the wind farm collection network, as well as the adjustment sensitivity of each equivalent wind farm to the voltage at the wind farm grid connection point in the equivalent circuit model. The primary reactive power support module is used to obtain the real-time grid connection point voltage of the wind farm. When the real-time grid connection point voltage of the wind farm is lower than the voltage drop threshold and the SVG has not reached the upper limit of reactive power, the current reactive power demand is determined according to the real-time grid voltage and the fitted equation, and the SVG is activated to provide primary reactive power support according to the current reactive power demand. The secondary reactive power support module is used to determine the reactive power output weight of each equivalent wind turbine unit by means of the adjustment sensitivity of each equivalent wind farm to the voltage at the grid connection point of the wind farm when the real-time wind farm grid connection point voltage is lower than the voltage drop threshold and the SVG reaches the upper limit of reactive power. Based on the reactive power output weight and the current reactive power demand, the wind turbine unit is started to provide secondary reactive power support.

10. A reactive power and voltage graded control device suitable for wind farm SVG, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 to 8.

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