CN109617116B - Wind power plant group impedance analysis method, reactive power control method and device and power generation system - Google Patents

Abstract

The invention discloses a wind farm group impedance analysis method, reactive power control method, device and power generation system. Among them, the wind farm group includes multiple wind turbines, and multiple wind turbines are connected to form multiple target control points. The target control points include the grid connection points and branch points of the wind farm group. The wind farm group impedance analysis method includes: According to the wind farm group According to the wind farm structure and wind field parameters, a simulation model of the wind farm group is established; according to the current voltage, current active power and current reactive power of the target control point of the wind farm group, the current working conditions of the target control point are determined; according to the simulation model, Determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current working conditions; correct the system impedance based on the small disturbance method and power flow distribution. According to the embodiments of the present invention, the measurement error of the system impedance can be reduced, and when performing reactive power control on the wind farm group, the flexibility of controlling each wind turbine unit and the safety and stability of the power grid can be improved.

Description

Wind farm group impedance analysis method, reactive power control method and device, and power generation system

technical field

The invention belongs to the technical field of wind power, and in particular relates to a wind farm group impedance analysis method and a reactive power control method and device and a power generation system.

Background technique

In order to meet the increasing demand for power resources, the scale of wind farms needs to be increased. When the scale of the wind farm increases, not only the centralized access of large-scale wind turbines to the power system will have a great impact on the security and stability of the power grid, but also the fluctuation of the voltage at the grid connection point of the wind farm caused by the reactive power fluctuation will also directly affect The security and stability of the power grid. Specifically, as the scale of the wind farm increases, especially the capacity of the wind farm group increases, the output of the wind turbine will have a certain spatial coupling characteristic, so that the fluctuation of the reactive power of the wind farm will affect the stable operation of the power grid. to have a great impact.

According to the provisions of "GB/T 19963-2011 Technical Regulations for Wind Farm Access to Power System", wind turbines need to have a certain amount of reactive power when they are connected to the power system. Therefore, there are two main methods for reactive power control of wind farms. Each wind turbine itself controls and performs centralized reactive power compensation for the wind farm. When controlling each wind turbine itself, the free control of the wind turbines in the wind farm will cause the internal consumption of reactive power of the wind farm group, which cannot achieve the goal of giving priority to wind power generation efficiency. In the case of centralized reactive power compensation for wind farms, due to the disadvantages of high cost, large loss and poor stability of the centralized reactive power compensation equipment in wind farms, as well as the problem of poor coordination between the centralized reactive power compensation equipment and the wind turbine, it cannot be very Good realization of reactive power control.

SUMMARY OF THE INVENTION

In view of one or more of the above problems, embodiments of the present invention provide a wind farm group impedance analysis method and reactive power control method and device, and a power generation system.

On the one hand, an embodiment of the present invention provides an impedance analysis method for a wind farm group. The wind farm group includes multiple wind turbines, and the multiple wind turbines are connected to form multiple target control points. The target control points include grid-connected points and branches of the wind farm group. Waypoint, impedance analysis methods include:

According to the wind farm structure and wind farm parameters of the wind farm group, the simulation model of the wind farm group is established;

Determine the current working condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group;

According to the simulation model, determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating conditions;

According to the small disturbance method and the power flow distribution, the system impedance is corrected.

Further, according to the simulation model, determining the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating conditions includes:

Generate multiple operating conditions of the target control point according to the threshold combinations of multiple sets of voltage thresholds, active power thresholds and reactive power thresholds;

Based on the simulation model, the impedance data of the system impedance corresponding to the multiple working conditions of the target control point and the power flow data of the power flow distribution of the wind farm group corresponding to the multiple working conditions are obtained;

The system impedance of the target control point corresponding to the current working condition and the power flow distribution of the wind farm group corresponding to the current working condition are obtained from the impedance data and the power flow data.

Further, according to the small disturbance method and the power flow distribution, modifying the system impedance includes:

Based on the small disturbance method, the system impedance is corrected, and the corrected impedance of the target control point is obtained;

According to the power flow distribution, the reversed impedance of the target control point is obtained;

If the difference between the corrected impedance and the reversed impedance is less than or equal to the predetermined threshold, the system impedance is updated with the corrected impedance; if the difference between the corrected impedance and the reversed impedance is greater than the predetermined threshold, the system impedance of the target control point is reacquired and corrected.

On the other hand, an embodiment of the present invention provides a reactive power control method for a wind farm group, and the reactive power control method includes:

Obtain the current voltage, current active power and current reactive power of each target control point;

According to the above-mentioned wind farm group impedance analysis method, determine the system impedance of each target control point and the power flow distribution of the wind farm group;

Receive grid dispatch signals, and calculate the ideal reactive power of grid-connected points based on grid dispatch signals;

According to the ideal reactive power, the system impedance of each target control point and the power flow distribution of the wind farm group, allocate the reactive power to be supplied or absorbed to each wind turbine, and send a message to each wind turbine to instruct the wind turbine to generate the allocated Reactive power command.

Further, receiving the grid dispatching signal and calculating the ideal reactive power of the grid-connected point based on the grid dispatching signal includes:

Set the dead zone threshold of the grid connection point;

When the absolute value of the difference between the current voltage of the grid-connected point and the grid dispatch signal is greater than the dead zone threshold, the ideal reactive power of the grid-connected point is calculated using the formula for ideal reactive power.

Further, according to the ideal reactive power, the system impedance of each control point and the power flow distribution of the wind farm group, allocating the reactive power to be provided or absorbed to each wind turbine includes:

Determine the reactive power margin of reactive power compensation equipment;

Determine the objective function, inequality constraints and equality constraints based on reactive power margin, system impedance of each target control point and power flow distribution of wind farm groups;

Solve ideal reactive power, objective function, inequality constraints, and equality constraints, and assign reactive power to be provided or absorbed to each wind turbine.

Further, the objective function at least includes: the minimum network loss, the minimum voltage deviation, the minimum reactive power margin deviation and the weighted sum of the minimum network loss, the minimum voltage deviation and the minimum reactive power margin deviation of each target control point.

Further, the inequality constraints at least include: power flow equation inequality constraints, system safety inequality constraints, and reactive power inequality constraints for wind turbines and reactive power compensation equipment.

Further, the equation constraints at least include: grid connection point voltage equation constraints and power flow equation constraints.

In another aspect, an embodiment of the present invention provides an impedance analysis device for a wind farm group, where the wind farm group includes multiple wind turbines, the multiple wind turbines are connected to form multiple target control points, and the target control points include grid connection points of the wind farm group and branch points, including:

The model establishment unit is used to establish the simulation model of the wind farm group according to the wind farm structure and the wind farm parameters of the wind farm group;

The working condition determination unit is used to determine the current working condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group;

The simulation processing unit is used to determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current working conditions according to the simulation model;

The correction processing unit is used to correct the system impedance according to the small disturbance method and the power flow distribution.

Further, the simulation processing unit includes:

a working condition generating unit, configured to generate multiple working conditions of the target control point according to the threshold combinations of multiple sets of voltage thresholds, active power thresholds and reactive power thresholds;

A simulation computing unit, configured to obtain, based on the simulation model, impedance data of the system impedance of the target control point corresponding to the multiple working conditions and power flow data of the power flow distribution of the wind farm group corresponding to the multiple working conditions;

The result determination unit is used to obtain the system impedance of the target control point corresponding to the current working condition and the power flow distribution of the wind farm group corresponding to the current working condition from the impedance data and the power flow data.

Further, the correction processing unit includes:

The correction calculation unit is used to correct the system impedance based on the small disturbance method to obtain the corrected impedance of the target control point;

The system inversion unit is used to infer the inversion impedance of the target control point according to the power flow distribution;

The correction decision-making unit is used to update the system impedance with the corrected impedance if the difference between the corrected impedance and the reversed impedance is less than or equal to a predetermined threshold; if the difference between the corrected impedance and the reversed impedance is greater than the predetermined threshold, re-acquire and correct the target control point system impedance.

In another aspect, an embodiment of the present invention provides a reactive power control device for a wind farm group. The wind farm group includes a plurality of wind turbines, and the multiple wind turbines are connected to form a plurality of target control points. The target control points include a parallel connection of the wind farm group. Network points and branch points, reactive power control devices include:

The power grid detection module is used to obtain the current voltage, current active power and current reactive power of each target control point;

Communication interface, used to receive grid dispatch signals;

The above-mentioned wind farm group impedance analysis device is used for taking each target control point as the target control point respectively, and determining the system impedance of each control point and the power flow distribution of the wind farm group;

The grid strategy module is used to calculate the ideal reactive power of the grid connection point based on the grid dispatch signal;

The wind turbine control module is used to allocate the reactive power to be supplied or absorbed to each wind turbine according to the ideal reactive power, the system impedance of each target control point and the power flow distribution of the wind farm group, and to send instructions to each wind turbine. The wind turbine generates commands for the allocated reactive power.

Further, the power grid strategy module also includes:

The power calculation unit is preset with the dead zone threshold of the grid connection point, which is used to calculate and use the ideal reactive power calculation formula when the absolute value of the difference between the grid connection point voltage and the grid dispatch signal is greater than the dead zone threshold value. The ideal reactive power of the outlets.

Further, the fan control module includes:

The data acquisition unit is used to determine the reactive power margin of the reactive power compensation equipment;

Power distribution unit for determining the objective function, inequality constraints and equality constraints based on reactive power margin, system impedance of each target control point and power flow distribution of the wind farm group; and solving ideal reactive power, objective function, inequality Constraints and equation constraints to allocate the reactive power to be supplied or absorbed to each wind turbine.

In another aspect, an embodiment of the present invention provides a power generation system, including:

Multiple wind turbines set on the collection line, multiple wind turbines are connected to form multiple target control points, and the target control points include the grid connection point and branch point of the wind farm group; wherein, the branch point is connected to the low-voltage bus and passes through the transformer. After boosting, it is connected to the high-voltage bus, and the high-voltage bus is connected and sent out from the grid connection point;

According to the above-mentioned reactive power control device of a wind farm group, the detection devices and reactive power compensation equipment of each wind turbine group and each target control point are respectively connected via communication lines.

Therefore, on the one hand, the method and device for analyzing the impedance of a wind farm group according to the embodiments of the present invention can obtain the current voltage, current active power and current reactive power of the target control point of the wind farm group using the simulation model of the wind farm group. The system impedance of the target control point and the power flow distribution of the wind farm group, and the system impedance can be corrected according to the small disturbance method and the power flow distribution. Therefore, it can be avoided due to the on-site measurement of the system impedance of the target control point and the power flow distribution of the wind farm group. the problem of large errors.

On the other hand, the method and device for reactive power control of a wind farm group in the embodiments of the present invention can be based on the voltage, active power and reactive power of each target control point after acquiring the voltage, active power and reactive power of each target control point. Reactive power and simulation models are used to obtain the system impedance of each target control point and the power flow distribution of the wind farm group. Therefore, the reactive power loss and active power loss of the wind farm group as a whole can be reduced, and the economic efficiency of the farm and the power grid can be improved.

On the other hand, the reactive power control method and device for a wind farm group according to the embodiments of the present invention allocate reactive power by integrating ideal reactive power, system impedance of each target control point, and power flow distribution of the wind farm group. Fully considering the spatial coupling characteristics between each target control point in the wind farm group, therefore, the rationality of the power flow distribution of the wind farm group and the safety and stability of the power grid can be improved by improving the flexibility of the control of each wind farm group. , to avoid the oscillation of the grid voltage.

On the other hand, the reactive power control method and device for a wind farm group according to the embodiments of the present invention, by allocating reactive power to the wind turbines, controlling the wind turbines to actively emit appropriate reactive power, fully exerting the capabilities of each wind turbine, and can In the case of omitting centralized reactive power compensation and other equipment, the wind turbine can still be controlled to emit appropriate reactive power, which greatly reduces the utilization rate of centralized reactive power compensation equipment, thereby improving the safety and stability margin of the power grid and reducing centralized reactive power. Compensate for the cost of using the equipment.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments of the present invention. For those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

FIG. 1 is a schematic structural diagram of an example of a topology structure of a wind farm group;

2 is a schematic flowchart of an existing method for performing reactive power control on branch points;

3 is a schematic flowchart of a wind farm group impedance analysis method provided by an embodiment of the present invention;

Fig. 4 is a sub-flow diagram of one embodiment of step S330 in Fig. 3;

Fig. 5 is a sub-flow diagram of an embodiment of step S340 in Fig. 3;

6 is a schematic flowchart of a reactive power control method for a wind farm group provided by an embodiment of the present invention;

Fig. 7 is a sub-flow diagram of an embodiment of step S430 in Fig. 6;

Fig. 8 is a sub-flow diagram of an embodiment of step S440 in Fig. 6;

9 is a schematic structural diagram of a network topology with 6 nodes;

10 is a schematic structural diagram of the network topology between node i and node j in the network topology of FIG. 9;

11 is a schematic structural diagram of a wind farm group impedance analysis device provided by an embodiment of the present invention;

FIG. 12 is a schematic structural diagram of a reactive power control device for a wind farm group provided by an embodiment of the present invention.

Detailed ways

The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention, and are not configured to limit the present invention. It will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by illustrating examples of the invention.

It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprises" does not preclude the presence of additional identical elements in a process, method, article, or device that includes the element.

FIG. 1 shows a schematic structural diagram of an example of the topology of a wind farm cluster. As shown in Figure 1, the wind farm group includes five wind turbines 101, 102, 103, 104, 105. The wind turbine 101 is connected to the low-voltage bus through the control point C1, the wind turbine 102 is connected to the low-voltage bus through the control point C2, and the wind turbine is connected to the low-voltage bus through the control point C2. 103 and 104 are connected to the low-voltage bus through the control point C3, the wind turbine 105 is connected to the low-voltage bus through the control point C4, and then each low-voltage bus is connected to the high-voltage bus after being boosted by the transformer, and the high-voltage bus is connected by the control point C0-POC. grid. Among them, each wind turbine is equipped with a reactive power compensation device (Static Var Generator, SVG).

In order to maintain the safe and stable operation of the power grid corresponding to the wind farm group shown in Figure 1, it is necessary to ensure the stability of the voltage of the grid connection point (control point C0-POC) in the control point of the wind farm group (that is, the voltage of the G-section bus in the figure). . However, due to the mutual coupling between the branch points (control points C1, C2, C3, and C4) in the control points of the wind farm group, the currently used control points C1, C2, C3, and C4 of the wind farm group are respectively The reactive power control method that performs the reactive power control alone to indirectly realize the reactive power control of the control point C0-POC cannot have a better reactive power control effect.

FIG. 2 shows a schematic flowchart of a conventional method for reactive power control of branch points. As shown in Figure 2, the current method for controlling any one of the branch points is as follows:

S201, preset the system impedance of the branch point;

S202, obtaining the voltage Umeas of each branch point and obtaining the voltage control command Uset of the branch point through a communication device or a hardware device;

S203, determine whether the voltage Umeas of each branch point crosses the line according to the voltage Umeas of each branch point and the voltage control command Uset, if it crosses the line, then execute step S104, if it does not cross the line, then execute step S1/6;

S204, calculating the difference between the voltage control command Uset and the voltage Umeas of the branch point where the voltage Umeas crosses the line, to obtain the target reactive power of the branch point;

S205. Generate a reactive power command for the branch point according to the target reactive power of the branch point, and execute the reactive power command for the branch point through SVG;

S206, the fan replaces the SVG reactive power command.

In this reactive power control method, the system impedance is not obtained through acquisition or analysis, but is pre-set by the user for each branch point based on experience. Since the set system impedance may have a large error with the actual one, this makes In the subsequent analysis, the reactive power control of each branch point will be affected.

In addition, in the existing reactive power control method, since the reactive power control is performed on each branch point respectively, and multiple branch points are not considered comprehensively, the following problems may arise:

Since the control point C1 and the control point C2 are connected to the A-section bus, and the control point C3 and the control point C4 are connected to the C-section bus, there may be strong coupling between the control point C1 and the control point C2, and the control point C3 and the control point C4. There may also be strong coupling between them, and they have a great influence on each other. When using the current reactive power control method for the wind farm group to perform reactive power control on the wind farm group shown in Figure 1, when the distributed control is performed on each branch point (control points C1, C2, C3, C4), It may occur that while the control point C3 absorbs reactive power from the grid, the control point C4 will generate reactive power, that is, the reactive power control of the control point C3 and the control point C4 has a hedging phenomenon, resulting in wasted energy and reduced. The backup reactive power of the grid during a fault period. Likewise, the same problem exists between the control point C1 and the control point C2. Moreover, using the current reactive power control method for the wind farm group, when the wind farm group controls the grid-connected point (control point C0-POC) individually, the SVG will also absorb reactive power, and the wind turbine will emit reactive power. question.

More seriously, when the automatic voltage control (Automatic Voltage Control, AVC) system of control point C3 and control point C4 controls control point C3 and control point C4 respectively, if the control point set by the AVC system of the two control points The parameters are exactly the same, and there may also be a problem of voltage oscillation at the control point, which will cause the voltage at the grid-connected point (control point C0-POC) to oscillate, thus endangering the safe and stable operation of the power grid.

In addition to the method of setting the system impedance based on experience in the prior art described above, there is also a method for obtaining the system impedance of the target control point in the prior art, which specifically uses the voltage, active power and reactive power at two different times. Calculate the relationship between the powers, where the relationship between the voltage, active power and reactive power at two different times is:

According to the above formula, the calculation formula of the system impedance can be obtained as:

Among them, U ₁ , P ₁ , Q ₁ respectively represent the voltage, active power and reactive power of a control point at the previous moment, and U ₂ , P ₂ , Q ₂ respectively represent the voltage, active power and reactive power of the control point at the next moment. Reactive power, X represents the system impedance at that control point.

Although this method can reduce the error of using experience to set the system impedance to a certain extent, due to the uncertainty of the field test environment, when the power grid fluctuates, there will still be a large measurement error, which will affect the subsequent reactive power control.

In order to solve the above-mentioned problems in the prior art, the embodiments of the present invention provide a wind farm group impedance analysis method, a reactive power control method and device, and a power generation system. The following first introduces the method for analyzing the impedance of a wind farm group provided by the embodiment of the present invention.

The wind farm group to which the wind farm group impedance analysis method provided by the embodiment of the present invention is applied includes multiple wind turbines, and the multiple wind turbines are connected to form multiple target control points, and the target control points include grid connection points and branches of the wind farm group For the convenience of description, a detailed description will be made with reference to the wind farm cluster described in FIG. 1 .

FIG. 3 shows a schematic flowchart of a method for analyzing the impedance of a wind farm group provided by an embodiment of the present invention. As shown in Figure 3, the wind farm group impedance analysis method includes:

S310, establishing a simulation model of the wind farm group according to the wind farm structure and wind farm parameters of the wind farm group;

S320. Determine the current operating condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group;

S330, according to the simulation model, determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current working condition;

S340. Correct the system impedance according to the small disturbance method and the power flow distribution.

Therefore, the embodiment of the present invention can obtain the system impedance of the target control point and the power flow distribution of the wind farm group by using the simulation model of the wind farm group according to the current voltage, current active power and current reactive power of the target control point of the wind farm group, And the system impedance can be corrected according to the small disturbance method and the power flow distribution. Therefore, the problem of large errors that may be caused by the on-site measurement of the system impedance of the target control point and the power flow distribution of the wind farm group can be avoided.

In step S310 of the embodiment of the present invention, simulation software such as PSSE may be used to establish a simulation model of the wind farm group according to the wind farm structure and wind farm parameters of the wind farm group.

In step S320 of the embodiment of the present invention, the current voltage, current active power and current reactive power of the target control point may be acquired, and the current operating condition is combined with the detected values of the current voltage, current active power and current reactive power.

FIG. 4 shows a sub-flow chart of an embodiment of step S330 in FIG. 3 . As shown in Figure 4, in step S330, according to the simulation model, a specific method for determining the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating conditions may include:

S331. Generate multiple operating conditions of the target control point according to multiple sets of threshold combinations of voltage thresholds, active power thresholds, and reactive power thresholds;

S332. Obtain, based on the simulation model, the impedance data of the system impedance of the target control point corresponding to the multiple working conditions and the power flow data of the power flow distribution of the wind farm group corresponding to the multiple working conditions;

S333 . Obtain the system impedance of the target control point corresponding to the current working condition and the power flow distribution of the wind farm group corresponding to the current working condition from the impedance data and the power flow data.

In step S331 of this embodiment of the present invention, all possible voltage thresholds, active power thresholds, and reactive power thresholds may be listed, and these voltage thresholds, active power thresholds, and reactive power thresholds may be combined in a variety of possible combinations, Obtain multiple sets of threshold combinations, which are generated by different voltage thresholds, active power thresholds and reactive power thresholds, each set of threshold combinations can be determined as a working condition, that is, each set of voltage thresholds, active power thresholds Threshold and reactive power threshold are one working condition.

In step S332 of this embodiment of the present invention, different combinations of thresholds may be input into the simulation model to obtain impedance data of the system impedance corresponding to multiple working conditions of the target control point and the wind farm group corresponding to multiple working conditions The power flow data of the power flow distribution.

Specifically, the system impedances corresponding to the target control points and multiple operating conditions can be generated through the simulation model based on all possible threshold combinations of the target control points, and these threshold combinations and the corresponding system impedances can be saved as a list to form power flow data, which is convenient for Follow-up query of the system impedance of the current working condition. In addition, in order to ensure the convergence of the calculation results, the power flow distribution of each operating condition can be generated through the simulation model based on all possible threshold combinations of the target control points, and these threshold combinations and the corresponding power flow distributions can be saved as a list to form the power flow data. In order to increase the speed of operation, ensure that the equations described later have solutions.

In step S333 of the embodiment of the present invention, the impedance data and the power flow data may be queried according to the combination of the current voltage, the current active power, and the current reactive power detection value for the current working condition, so that according to different working conditions and different The corresponding relationship between system impedance and power flow distribution, query to obtain the system impedance and power flow distribution corresponding to the current working condition.

It should be noted that, in the embodiments of the present invention, the actual values of the voltage thresholds, active power thresholds, and reactive power thresholds of each group are used as a working condition. The threshold value, active power threshold value and reactive power threshold value are processed, and the processed result is regarded as a working condition. At the same time, when determining the current working condition, the same function can also be used to process the current voltage, current active power and The current reactive power, as long as it is possible to obtain the simulated system impedance through the collected current voltage, current active power, and current reactive power.

FIG. 5 shows a sub-flow chart of an embodiment of step S340 in FIG. 3 . As shown in Figure 5, step S340, according to the small disturbance method and the power flow distribution, modifying the system impedance includes:

S341, correcting the impedance of the system based on the small disturbance method to obtain the corrected impedance of the target control point;

S342, inversely infer the target control point according to the power flow distribution;

S343. If the difference between the corrected impedance and the reversed impedance is less than or equal to a predetermined threshold, update the system impedance with the corrected impedance;

S344. If the difference between the corrected impedance and the reversed impedance is greater than a predetermined threshold, re-acquire and correct the system impedance of the target control point.

In actual work, the reactive power and voltage of the target control point will have a small fluctuation in real time. Therefore, in step S341, the corrected impedance of the control point can be calculated according to this small fluctuation, that is, the system impedance is corrected by the small disturbance method. . Specifically, the small disturbance method is a method of calculating the average value of the system impedance within a certain period of time after detecting the system impedance of the control point, and using the average value as the corrected impedance of the control point. Using the small perturbation method, the accuracy of the corrected impedance can be improved.

In order to further improve the accuracy of the system impedance used in the calculation described later, in step S342 , the reversed impedance of the control point can be obtained by inversely using the power flow distribution of the wind farm group as a reference value.

Then, compare the modified impedance with the reversed impedance: in step S343, if the difference between the modified impedance and the reversed impedance is less than or equal to a predetermined threshold, then use the modified impedance to update the system impedance, and use the modified impedance as the calculation described later The system impedance of the control point used in . In step S344, if the difference between the corrected impedance and the reversed impedance is greater than the predetermined threshold, all operations of steps S130 and S140 need to be re-executed.

Therefore, in the embodiment of the present invention, the system impedance and power flow distribution of each target control point can be obtained accurately. In addition, when the reactive power control of each cycle or each different working condition is performed, the system impedance and power flow distribution under the working condition corresponding to the moment can be updated, so as to avoid affecting the effect of reactive power control on the wind farm group.

FIG. 6 shows a schematic flowchart of a reactive power control method for a wind farm group provided by an embodiment of the present invention. As shown in Figure 6, the reactive power control method includes:

S410, obtaining the current voltage, current active power and current reactive power of each target control point;

S420, according to the above wind farm group impedance analysis method, determine the system impedance of each target control point and the power flow distribution of the wind farm group;

S430. Receive a grid dispatching signal, and calculate the ideal reactive power of the grid-connected point based on the grid dispatching signal;

S440. According to the ideal reactive power, the system impedance of each target control point, and the power flow distribution of the wind farm group, allocate the reactive power to be provided or absorbed to each wind turbine, and send a message to each wind turbine to instruct the wind turbine to generate Allocated reactive power command.

In the embodiment of the present invention, after obtaining the current voltage, current active power and current reactive power of each target control point, it is possible to obtain each target control point based on the current voltage, current active power, current reactive power and simulation model of each target control point. The system impedance of the target control point and the power flow distribution of the wind farm group, and when calculating the ideal reactive power according to the grid dispatch signal, according to the ideal reactive power, the system impedance of each target control point and the power flow distribution of the wind farm group to be Wind turbines distribute reactive power. Therefore, the overall reactive power loss and active power loss of the wind farm group can be reduced, the rationality of the power flow distribution of the wind farm group and the safety and stability of the power grid can be improved, and the oscillation of the power grid voltage can be avoided.

In step S410 of the embodiment of the present invention, the current voltage U and current current I of the control points C1, C2, C3, C4, C0-POC of the wind farm group shown in FIG. The current I calculates the current active power P and the current reactive power Q. Besides, the current power factor Cos can also be calculated according to the current voltage U and the current current I.

In step S420, simulation software such as PSSE can be used to establish a simulation model of the wind farm group as shown in FIG. 1, and the above-mentioned wind farm group impedance analysis method can be used to determine each target control point C1, C2, C3, C4, C0 – The system impedance of the POC and the power flow distribution of the wind farm cluster.

In the existing method for obtaining the system impedance, the system impedance of the control point is only obtained once when the reactive power control is performed for the first time, and after the system impedance is obtained, the reactive power control related to the reactive power control is carried out under all operating conditions. The system impedance is no longer changed during the calculation of , which will lead to inaccurate reactive power control of the wind farm group, especially when the operation mode of the wind farm group changes, the actual system impedance changes very significantly. At this time, continue Using a fixed value of system impedance creates serious control problems. Therefore, in the embodiment of the present invention, through the simulation model and the current voltage, current active power and current reactive power of each target control point, reasonable system impedance values of the target control point under different working conditions can be obtained, so as to avoid causing wind farm damage. Serious fluctuations in the reactive power control of the group.

In step S420 of the embodiment of the present invention, the embodiment of the present invention uses the thinking of big data to obtain the system impedance of each target control point and the power flow distribution of the wind farm group through the simulation model. Specifically, the current voltage U, current active power P and current reactive power Q of the collected target control points C1, C2, C3, C4, C0-POC can be taken as the current operating condition, and then in the impedance data and power flow data Perform a query to find the system impedance corresponding to the current working condition of the target control point and the power flow distribution corresponding to the current working condition of the wind farm group.

FIG. 7 shows a sub-flow chart of an embodiment of step S430 in FIG. 6 . As shown in FIG. 7 , in step S430, a specific method for receiving the grid dispatching signal and calculating the ideal reactive power of the grid-connected point based on the grid dispatching signal includes:

S431. Set the dead zone threshold of the grid-connected point;

S432 , when the absolute value of the difference between the current voltage of the grid-connected point and the grid dispatch signal is greater than the dead zone threshold, calculate the ideal reactive power of the grid-connected point by using a formula for calculating ideal reactive power.

In step S432, the ideal reactive power may be determined according to the current voltage of the grid connection point, the voltage control command corresponding to the grid dispatch signal, and the dead zone threshold.

For example, when the voltage Umeas of the grid-connected point exceeds the dead zone threshold U _db of the voltage control command Uset, the relationship between the voltage Umeas, the voltage control command Uset, and the dead zone threshold U _db is:

fabs(Umeas-Uset)>U _db

The ideal reactive power required by the grid connection point can be calculated according to the above formula:

It should be noted that when the absolute value of the difference between the current voltage of the grid connection point and the grid dispatch signal is less than or equal to the dead zone threshold, there is no need to re-allocate the reactive power to be provided or absorbed to each wind turbine.

FIG. 8 shows a sub-flow chart of an embodiment of step S440 in FIG. 6 . As shown in FIG. 8, in step S440, according to the ideal reactive power, the system impedance of each target control point and the power flow distribution of the wind farm group, the specific method of allocating the reactive power to be provided or absorbed to each wind turbine may include:

S441. Determine the reactive power margin of the reactive power compensation equipment;

S442, determining the objective function, inequality constraints and equality constraints based on reactive power margin, system impedance of each target control point, and power flow distribution of the wind farm group;

S443 , solving the ideal reactive power, the objective function, the inequality constraints and the equation constraints, and assigning the reactive power to be provided or absorbed to each wind turbine.

In the embodiment of the present invention, the objective function may specifically include: the weighted sum of the minimum network loss, the minimum voltage deviation, the minimum reactive power margin deviation and the minimum network loss, the minimum voltage deviation and the minimum reactive power margin deviation of each target control point ; The inequality constraints can specifically include: power flow equation inequality constraints, system safety inequality constraints, reactive power inequality constraints for wind turbines and reactive power compensation equipment; equation constraints can specifically include: grid-connected point voltage equation constraints and power flow equation constraints.

In other embodiments, the objective function is one or more of the minimum network loss, the minimum voltage deviation, the minimum reactive power margin deviation and the weighted sum of the minimum network loss, the minimum voltage deviation and the minimum reactive power margin deviation of each target control point. The inequality constraints can be one or more of the power flow equation inequality constraints, system safety inequality constraints, and reactive power inequality constraints for wind turbines and reactive power compensation equipment; the equation constraints can be grid-connected point voltage, etc. One or more of the equation constraints and the power flow equation constraints.

Hereinafter, a specific method of step S340 in the embodiment of the present invention will be described according to a specific reactive power optimization scheduling algorithm.

The optimal reactive power scheduling (ORPD) can be obtained by using the reactive power optimization scheduling algorithm. ORPD is one of the core problems of power distribution system operation, which can effectively reduce system power loss, reduce operating risks, and improve power quality. However, the original ORPD is a non-deterministic polynomial problem that is difficult to solve directly. In this example, a second-order cone (SOC) can be applied to relax the ORPD model to a convex second-order cone programming (SOCP) model and then solved.

In order to simultaneously satisfy the voltage requirements of multiple control points (C1C2C3C4), as well as other control objectives, according to the voltage, reactive power, active power and voltage reference related to the system impedance of each target control point and the power flow distribution of the wind farm group, adopt The following reactive power optimization scheduling algorithm:

(1) Select the objective function.

(i) Minimum network loss, (ii) Minimum voltage deviation, (iii) Minimum reactive power margin deviation, (iv) Minimum weighted sum of the above three objective functions.

Specifically:

(i)

(ii)

(iii)

(iv)

Among them, n _B and n _W are the number of all nodes and control points in the wind farm group; the set Φ(i) is the end node set of the branch with i as the head node in the power grid; r _ij is the resistance of the branch ij; i _ij is the current amplitude of the branch ij; _ui is the voltage amplitude of the node i; q _{j, svg} is the reactive power output by the SVG on the node i; η ₁ , η ₂ and η ₃ are the weights.

(2) Using the DistFlow method to calculate the constraints of the power flow equation of the radial distribution network.

FIG. 9 shows a schematic structural diagram of a network topology with 6 nodes. In the network topology shown in Figure 8, there is the following power flow constraint equation for node j:

Among them, p _1j and q _1j , p _2j and q _2j are the active power and reactive power injected by the head ends of branches 1j and 2j respectively; p _j3 and q _j3 , p _j4 and q _j4 are the heads of branches j3 and j4 respectively active power and reactive power injected at the terminal; p _j and q _j are the net active load and reactive load of node j, respectively; r _1j and x _1j , r _2j and x _2j are the resistance and reactance of branches 1j and 2j, respectively .

According to the characteristics of the power flow constraint equation, the equation of node j can be written as:

p _j = p _j,d -p _j,w (8)

q _j =p _j,d -q _j,w -q _j,svg (10)

Among them, Ω(j) is the set of head-end nodes of the branch with j as the end node in the network; set Φ(j) is the set of end nodes of the branch with j as the head-end node in the network; p _ij and q _ij are respectively The active power and reactive power injected at the head end of branch ij; p _j and q _j are the net load active power and reactive power of node j, respectively; p _j,w and p _j,d are respectively connected to node j Wind turbine output active power and load active power; q _j,w , q _j,svg and q _j,d are the wind turbine output reactive power, SVG output reactive power and load reactive power respectively connected to node j; _ui is the voltage amplitude of node i; r _ij and x _ij are the resistance and reactance of branch ij, respectively.

(3) Calculate the voltage constraint condition of the branch ij in Fig. 9 .

FIG. 10 shows a schematic structural diagram of the network topology between node i and node j in the network topology of FIG. 9 . As shown in Figure 10, the voltage constraint equation of branch ij is:

Among them, U _i is the voltage of node i, U _j is the voltage of node j, Z _ij is the impedance between node i and node j, I _ij is the current from node i to node j, S _ij is node i to node j the apparent power.

Taking the square of the modulo on both sides of equation (11) and expanding, we can get:

Assuming that the relative phase angle difference between nodes i and j is small and both are close to 0, we can obtain:

Among them, u _i and u _j are the voltage amplitudes of nodes i and j; r _ij and x _ij are the resistance and reactance of branch ij, respectively.

(4) Calculate the voltage constraint conditions of the grid connection point of the wind farm group.

The grid-connected voltage constraints are:

Among them, u ₀ is the voltage control command corresponding to the grid dispatch signal.

(5) The safety constraints of the computing system include voltage and current constraint equations.

The system security constraints are:

和

分别为节点j电压幅值上下限值；

和

为支路ij电流幅值上下限值。Among them, u _j and i _ij are the voltage amplitude of node j and the current amplitude of branch ij, respectively;

and

are the upper and lower limits of the voltage amplitude of node j, respectively;

and

is the upper and lower limits of the current amplitude of the branch ij.

(6) Calculate the output/absorb reactive power constraint conditions of the wind turbine and reactive power compensation equipment through the node j shown in FIG. 9 .

The reactive power constraints of wind turbines and reactive power compensation equipment are:

为风电机组无功功率输出上限值；p_j,w为节点j实际有功功率输出；α为风电场正常工作情况下功率因素，-0.95～0.95；

为SVG无功功率输出上限值；η为SVG容量的配置因子，一般取η＝0.2。c_j,w为节点j上所连的风电机组的装机容量。但是，上述模型存在风电机组和SVG无功功率异向问题。Among them, q _j,w and q _j,vsg are the reactive power output of the wind turbine and SVG connected to node j;

is the upper limit value of the reactive power output of the wind turbine; p _{j, w} is the actual active power output of node j; α is the power factor under normal working conditions of the wind farm, -0.95 to 0.95;

is the upper limit of SVG reactive power output; η is the configuration factor of SVG capacity, generally taking η=0.2. c _j,w is the installed capacity of the wind turbines connected to node j. However, the above model has the problem of anisotropy of reactive power of wind turbine and SVG.

Here, the slack variable s∈{0,1} is introduced, and the above model is transformed into:

(7) According to the characteristics of SOCP, take the power flow equation as SOCP relaxation, the formula (7), formula (9), and formula (15) can be defined as follows:

Among them, V _i represents the square of the voltage of any node i, and I _ij represents the square of the current between any two adjacent nodes i and node j, that is, the square of the current from node i to node j. After replacing the square with _Vi and I _ij , the formula can be made linear, which is convenient for calculation.

Then the above model can be transformed into:

After the above deformation, the power flow equation calculated by the Distflow method has become a linear equation system (27)-(29) and a simple quadratic equation (30).

For any small non-negative constant ε ≥ 0, we have

After further equivalent deformation, transform (32) into a standard second-order cone, we can get:

It has been proved by literature that the above second-order cone relaxation transformation process is strictly accurate in the radial distribution network model when the objective function of the embodiment of the present invention is a convex function and a strictly increasing function.

In summary, after the above deformation, the original ORPD becomes a problem of solving the following equation:

Objective function: formula (1)-(4);

Equality constraints: formula (16), formula (27)-(29);

Inequality constraints: formula (17)-(19), formula (21), formula (23), formula (24), formula (33).

The optimization model composed of the above formula, if the discrete control variables that may exist in the reactive power compensation equipment such as parallel capacitors are not considered, its objective function is linear, and all the equation constraints in the constraints are linear, except (33) Inequality constraints other than are also linear. However, the inequality in the mathematical form of Equation (33) just satisfies the definition of a second-order cone, that is, the above problem is a second-order cone programming problem and has excellent mathematical properties. Therefore, by solving the above formula, the reactive power to be provided or absorbed can be allocated to each wind turbine more accurately.

It should be noted that, due to engineering reasons, after obtaining the reactive power of each wind turbine and SVG according to the objective function, each wind turbine and SVG do not directly accept the direct dispatch of the AVC system of the grid-connected point in the target control point. Therefore, it is necessary to send the reactive power control command to the AVC system of each target control point, so that the AVC system of each target control point accepts the reactive power control command issued by the AVC system of the main grid connection point, and then the AVC system of each target control point The system then sends the reactive power control command to the corresponding wind turbine or SVG for execution, thereby realizing the reactive power control of the wind farm group.

It should be noted that although the reactive power control method in the embodiment of the present invention is described based on the wind farm group shown in FIG. 1 , the wind farm group to which the embodiment of the present invention can be applied is not limited to this, and can be applied to any wind farm group with The wind farm group of multiple wind turbines can also be applied to the reactive power control of a single wind turbine.

FIG. 11 shows a schematic structural diagram of a wind farm group impedance analysis device provided by an embodiment of the present invention. As shown in Figure 11, the wind farm group impedance analysis device includes:

The model establishing unit 510 is configured to establish a simulation model of the wind farm group according to the wind farm structure and the wind farm parameters of the wind farm group;

a working condition determining unit 520, configured to determine the current working condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group;

The simulation processing unit 530 is configured to determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current working condition according to the simulation model;

The correction processing unit 540 is configured to correct the system impedance according to the small disturbance method and the power flow distribution.

In this embodiment of the present invention, the simulation processing unit 530 may further include:

a working condition generating unit 531, configured to generate multiple working conditions of the target control point according to the threshold combinations of multiple sets of voltage thresholds, active power thresholds and reactive power thresholds;

The simulation calculation unit 532 is configured to obtain, based on the simulation model, the impedance data of the system impedance of the target control point corresponding to the multiple working conditions and the power flow data of the power flow distribution of the wind farm group corresponding to the multiple working conditions;

The result determination unit 533 is configured to obtain, from the impedance data and the power flow data, the system impedance of the target control point corresponding to the current working condition and the power flow distribution of the wind farm group corresponding to the current working condition.

In this embodiment of the present invention, the correction processing unit 540 may further include:

The correction calculation unit 541 is used to correct the system impedance based on the small disturbance method to obtain the corrected impedance of the target control point;

The system inversion unit 542 is used to infer the inversion impedance of the target control point according to the power flow distribution;

The correction decision unit 543 is used to update the system impedance with the corrected impedance if the difference between the corrected impedance and the reversed impedance is less than or equal to a predetermined threshold; if the difference between the corrected impedance and the reversed impedance is greater than the predetermined threshold, re-acquire and correct the target control point system impedance.

FIG. 12 shows a schematic structural diagram of a reactive power control device for a wind farm group provided by an embodiment of the present invention. As shown in Figure 12, the reactive power control device includes:

The grid detection module 610 is used to obtain the current voltage, current active power and current reactive power of each target control point;

a communication interface 620 for receiving grid dispatch signals;

The above-mentioned wind farm group impedance analysis device 630 is configured to use each target control point as a target control point, respectively, to determine the system impedance of each control point and the power flow distribution of the wind farm group;

a grid strategy module 640, configured to calculate the ideal reactive power of the grid-connected point based on the grid dispatch signal;

The wind turbine control module 650 is used for allocating the reactive power to be provided or absorbed to each wind turbine according to the ideal reactive power, the system impedance of each target control point and the power flow distribution of the wind farm group, and to send to each wind turbine the required power to be supplied or absorbed. A command instructing the wind turbine to generate the allocated reactive power.

In this embodiment of the present invention, the power grid strategy module 640 further includes:

The power calculation unit 641 is preset with a dead zone threshold of the grid-connected point, and is used to calculate the ideal value of the grid-connected point by using the calculation formula of ideal reactive power when the absolute value of the difference between the grid-connected point voltage and the grid dispatch signal is greater than the dead zone threshold reactive power.

In this embodiment of the present invention, the fan control module 650 includes:

a data acquisition unit 651, configured to determine the reactive power margin of the reactive power compensation device;

The power distribution unit 652 is used for determining the objective function, inequality constraints and equality constraints based on reactive power margin, system impedance of each target control point and power flow distribution of the wind farm group; and solving ideal reactive power, objective function, Inequality constraints and equality constraints allocate the reactive power to be supplied or absorbed to each wind turbine.

The embodiment of the present invention also provides a wind power generation system, including:

Multiple wind turbines set on the collection line, multiple wind turbines are connected to form multiple target control points, and the target control points include the grid connection point and branch point of the wind farm group; wherein, the branch point is connected to the low-voltage bus and passes through the transformer. After boosting, it is connected to the high-voltage bus, and the high-voltage bus is connected and sent out from the grid connection point;

According to the above-mentioned reactive power control device for wind farm groups, the detection devices and reactive power compensation equipment of each wind turbine group and each target control point are respectively connected via communication lines

To sum up, the main principle of the wind farm group impedance analysis method and the reactive power control method according to the embodiment of the present invention is to calculate the target (wind turbine) that needs to be optimized and controlled based on the global voltage/reactive power optimization control idea of the wind farm group. , using big data thinking to simulate and analyze different working conditions of the wind farm group in advance through the simulation model, and solve the system impedance and power flow distribution of each control point of the wind farm group under different working conditions, so that the small disturbance method can be used to solve the accurate The system impedance and the fast solution of the power flow distribution become possible, thus realizing the global reactive power control of the wind farm group.

The above are only specific implementations of the present invention. Those skilled in the art can clearly understand that, for the convenience and simplicity of the description, the specific working process of the above-described systems, modules and units may refer to the foregoing method embodiments. The corresponding process in , will not be repeated here. It should be understood that the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all cover within the protection scope of the present invention.

Claims (16)

1. An impedance analysis method for a wind farm group, wherein the wind farm group includes a plurality of wind turbines, the plurality of wind turbines are connected to form a plurality of target control points, and the target control points include a grid connection point of the wind farm group and branch points, characterized in that the impedance analysis method includes: establishing a simulation model of the wind farm group according to the wind farm structure and wind farm parameters of the wind farm group; Determine the current operating condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group; According to the simulation model, determine the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating condition; According to the small disturbance method and the power flow distribution, the system impedance is corrected. 2 . The impedance analysis method according to claim 1 , wherein, according to the simulation model, determining the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating conditions comprises: 3 . generating multiple operating conditions of the target control point according to multiple sets of threshold combinations of voltage thresholds, active power thresholds and reactive power thresholds; Obtain, based on the simulation model, impedance data of the system impedance of the target control point corresponding to the multiple operating conditions and power flow data of the power flow distribution of the wind farm group corresponding to the multiple operating conditions; The system impedance of the target control point corresponding to the current operating condition and the power flow distribution of the wind farm group corresponding to the current operating condition are obtained from the impedance data and the power flow data. 3. The impedance analysis method according to claim 1, wherein, according to the small disturbance method and the power flow distribution, modifying the system impedance comprises: Modify the system impedance based on the small disturbance method to obtain the modified impedance of the target control point; Reverse inference according to the power flow distribution to obtain the inverse impedance of the target control point; If the difference between the modified impedance and the reversed impedance is less than or equal to a predetermined threshold, use the modified impedance to update the system impedance; if the difference between the modified impedance and the reversed impedance is greater than the predetermined threshold , reacquire and correct the system impedance of the target control point. 4. A reactive power control method for a wind farm group, wherein the reactive power control method comprises: Obtain the current voltage, current active power and current reactive power of each target control point; According to the wind farm group impedance analysis method according to any one of claims 1-3, the system impedance of each of the target control points and the power flow distribution of the wind farm group are determined; receiving a grid dispatch signal, and calculating the ideal reactive power of the grid-connected point based on the grid dispatch signal; According to the ideal reactive power, the system impedance of each of the target control points, and the power flow distribution of the wind farm group, the reactive power to be supplied or absorbed is allocated to each of the wind turbines, and the reactive power to be supplied to each of the wind turbines is allocated to each of the wind turbines. An instruction is sent to instruct the wind turbine to generate the allocated reactive power. 5 . The reactive power control method according to claim 4 , wherein receiving a grid dispatch signal and calculating the ideal reactive power of the grid connection point based on the grid dispatch signal comprises: 6 . Set the dead zone threshold of the grid-connected point; When the absolute value of the difference between the current voltage of the grid-connected point and the grid dispatch signal is greater than the dead zone threshold, the ideal reactive power of the grid-connected point is calculated by using the formula for calculating ideal reactive power . 6 . The reactive power control method according to claim 4 , wherein, according to the ideal reactive power, the system impedance of each of the target control points, and the power flow distribution of the wind farm group, each of the wind power The reactive power to be provided or absorbed by the unit distribution includes: Determine the reactive power margin of reactive power compensation equipment; determining an objective function, inequality constraints, and equality constraints based on the reactive power margin, the system impedance of each of the target control points, and the power flow distribution of the wind farm group; The ideal reactive power, the objective function, the inequality constraints, and the equation constraints are solved, and the reactive power to be provided or absorbed is allocated to each of the wind turbines. 7 . The reactive power control method according to claim 6 , wherein the objective function at least comprises: the minimum network loss, the minimum voltage deviation, the minimum reactive power margin deviation and the minimum network loss of each of the target control points. 8 . Weighted sum of network losses, said minimum voltage deviation and said minimum reactive margin deviation. 8. The reactive power control method according to claim 6, wherein the inequality constraints at least include: power flow equation inequality constraints, system safety inequality constraints, reactive power inequality of wind turbines and reactive power compensation equipment Restrictions. 9 . The reactive power control method according to claim 6 , wherein the equation constraints at least include: grid connection point voltage equation constraints and power flow equation constraints. 10 . 10. An impedance analysis device for a wind farm group, the wind farm group comprising a plurality of wind turbines, the plurality of wind turbines being connected to form a plurality of target control points, the target control points comprising a grid connection point of the wind farm group and branch points, characterized in that they include: a model establishing unit for establishing a simulation model of the wind farm group according to the wind farm structure and wind farm parameters of the wind farm group; a working condition determining unit, configured to determine the current working condition of the target control point according to the current voltage, current active power and current reactive power of the target control point of the wind farm group; a simulation processing unit, configured to determine, according to the simulation model, the system impedance of the target control point and the power flow distribution of the wind farm group under the current operating condition; A correction processing unit, configured to correct the system impedance according to the small disturbance method and the power flow distribution. 11. The impedance analysis device according to claim 10, wherein the simulation processing unit comprises: a working condition generating unit, configured to generate multiple working conditions of the target control point according to the threshold combinations of multiple sets of voltage thresholds, active power thresholds and reactive power thresholds; A simulation computing unit, configured to obtain, based on the simulation model, the impedance data of the system impedance of the target control point corresponding to the multiple operating conditions and the power flow distribution of the wind farm group corresponding to the multiple operating conditions tidal current data; A result determination unit, configured to obtain, from the impedance data and the power flow data, the system impedance of the target control point corresponding to the current operating condition and the power flow of the wind farm group corresponding to the current operating condition distributed. 12. The impedance analysis device according to claim 10, wherein the correction processing unit comprises: a correction calculation unit, configured to correct the system impedance based on the small disturbance method to obtain the corrected impedance of the target control point; a system inversion unit, configured to infer the inverse impedance of the target control point according to the power flow distribution; A correction decision unit, configured to update the system impedance by using the corrected impedance if the difference between the corrected impedance and the reversed impedance is less than or equal to a predetermined threshold; if the difference between the corrected impedance and the reversed impedance is If the value is greater than the predetermined threshold, the system impedance of the target control point is reacquired and corrected. 13. A reactive power control device for a wind farm group, the wind farm group comprising a plurality of wind turbines, the plurality of wind turbines being connected to form a plurality of target control points, the target control points comprising the parallel of the wind farm group. Network point and branch point, characterized in that the reactive power control device includes: a power grid detection module for acquiring the current voltage, current active power and current reactive power of each of the target control points; Communication interface, used to receive grid dispatch signals; The wind farm group impedance analysis device according to any one of claims 10-12, which is used for determining the system impedance of each of the control points and the power flow distribution of the wind farm group; a grid strategy module, configured to calculate the ideal reactive power of the grid-connected point based on the grid dispatch signal; A wind turbine control module, configured to allocate reactive power to be provided or absorbed to each of the wind turbines according to the ideal reactive power, the system impedance of each of the target control points, and the power flow distribution of the wind farm group, and Instructions are sent to each of the wind turbines instructing the wind turbines to generate the allocated reactive power. 14. The reactive power control device according to claim 13, wherein the power grid strategy module further comprises: A power calculation unit, where a dead zone threshold of the grid-connected point is preset in the power calculation unit, for when the absolute value of the difference between the grid-connected point voltage and the grid dispatch signal is greater than the dead zone threshold, The ideal reactive power of the grid-connected point is calculated by using the calculation formula of the ideal reactive power. 15. The reactive power control device according to claim 13, wherein the fan control module comprises: The data acquisition unit is used to determine the reactive power margin of the reactive power compensation equipment; a power distribution unit for determining an objective function, inequality constraints, and equality constraints based on the reactive power margin, the system impedance of each of the target control points, and the power flow distribution of the wind farm group; and solving the ideal The reactive power, the objective function, the inequality constraints, and the equality constraints allocate the reactive power to be provided or absorbed to each of the wind turbines. 16. A power generation system, comprising: A plurality of wind turbines arranged on the collection line, the plurality of wind turbines are connected to form a plurality of target control points, and the target control points include the grid connection point and the branch point of the wind farm group; wherein, the branch road The point is connected to the low-voltage bus, and after being boosted by the transformer, it is connected to the high-voltage bus, and the high-voltage bus is connected to the outgoing line by the grid connection point; According to the reactive power control device for a wind farm group according to any one of claims 13-15, the detection devices and reactive power compensation equipment of each wind turbine group, each target control point are respectively connected via communication lines.

Images