CN105406458B - A kind of wind-powered electricity generation collects the practical appraisal procedure of system ability of supplying electric power and device - Google Patents

Abstract

The present invention relates to a practical evaluation method and device for the power transmission capacity of a wind power collection system, wherein the evaluation method is suitable for a dynamic reactive power compensation device, and the dynamic reactive power compensation device adopts a purely inductive branch constant reactive power control, and the method Including: obtaining the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch; inputting a single set of fixed capacitors, and obtaining the input single set of fixed capacitors according to the voltage-reactive power sensitivity of the wind power collection system. According to the range of voltage change of the input single set of fixed capacitor compensation, the necessary conditions for the controllable voltage fluctuation of the wind power collection system are obtained; according to the necessary conditions for the controllable voltage fluctuation of the wind power collection system, the wind power collection system Practical evaluation and correction equation of electric capacity; the practical evaluation of power transmission capacity of the wind power collection system is realized by using the correction equation for practical evaluation of the power transmission capacity of the wind power collection system.

Description

A practical evaluation method and device for power transmission capacity of a wind power collection system

technical field

The invention relates to the field of power transmission capacity evaluation, in particular to a practical evaluation method and device for the power transmission capacity of a wind power collection system.

Background technique

With the increase of wind power grid-connected capacity year by year, the economic dispatch and safe operation of the power grid are facing great challenges. Accurately evaluating the power transmission capacity of the actual wind power system is not only an important means to prevent the system operating point from approaching or reaching the static voltage stability limit, but also a key method to ensure that the system voltage adjustment sensitivity is normal and controllable. Under normal operating conditions, it is required that the change in bus voltage caused by the switching of the largest single reactive power compensation device in the system should not exceed 2.5% of the rated voltage.

As shown in FIG. 1 , it is a schematic diagram of an equivalent circuit of a traditional wind power collection system. The typical structure of my country's wind power system can be equivalent to the circuit in Figure 1, and the wind power collection system is simulated by a single wind farm. In Fig. 1, E: external equivalent infinite bus voltage; V: grid-connected bus voltage of wind farm; P: active power sent out by wind farm; Q _c : compensation capacity of single fixed capacitor; Q _L : dynamic reactive power compensation device The initial reactive power absorbed by the inductive branch; X: the equivalent reactance of the transmission line; the evaluation equation of the current transmission capacity of the existing wind power collection system needs to be derived by means of the static voltage sensitivity method, and the influence of the dynamic characteristics of the controller is not considered.

Assuming that the capacity of a single group of reactive power compensation devices is Q _c , the controllable voltage variation range in stable operation cannot exceed ξ. When the influence of the control of the dynamic reactive power compensation device is not considered, its inductive branch can be regarded as a fixed inductance, so the static voltage sensitivity formula (such as formula 1) is obtained, and the necessary conditions for static voltage controllability are deduced as formula 2:

Finally, the evaluation equation of the transmission capacity of the wind power collection system that does not take into account the influence of the control of the dynamic reactive power compensation device is deduced from Equation 2, as shown in Equation 3:

Since the existing evaluation equation of wind power system power transmission capacity does not consider the influence of dynamic reactive power compensation device control in the wind farm, the estimation result of this evaluation equation is not accurate, which may easily lead to overestimation of the actual wind power system power transmission capacity, resulting in The excessive sensitivity of the system voltage adjustment causes the consequences of voltage fluctuations exceeding ξ after compensation by a single group of capacitors, which seriously threatens the stable operation of the system.

At present, the derivation of the evaluation equation for the active power delivery capability of large-scale wind power collection systems is mostly based on the static voltage sensitivity method of the wind power access system. In fact, there are many types of reactive power sources in the wind farm. In addition to static capacitors, dynamic reactive power compensation devices It is also widely used, so the wind power system transmission capacity evaluation equation that only considers static characteristics and does not take into account the influence of dynamic reactive power compensation device control is inaccurate, which may cause overestimation of wind power system transmission capacity and threaten system security.

Contents of the invention

In order to solve the above technical problems, the present invention proposes a practical evaluation method and device for the power transmission capacity of the wind power collection system, which avoids the inconsistency of the power transmission capacity evaluation equation of the wind power system that does not take into account the influence of the control of the dynamic reactive power compensation device in the prior art. Accuracy may lead to an overestimation of the output capacity of the wind power system.

In order to achieve the above purpose, the present invention provides a practical evaluation method for the power transmission capacity of the wind power collection system, which is characterized in that the evaluation method is suitable for a dynamic reactive power compensation device, and the dynamic reactive power compensation device adopts a purely inductive branch constant reactive power power control, the method comprising:

Obtain the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch;

Put in a single set of fixed capacitors, and obtain the range of voltage change caused by the compensation of the input single set of fixed capacitors according to the voltage-reactive power sensitivity of the wind power collection system, and obtain the range of voltage changes caused by the input of a single set of fixed capacitors after compensation. Necessary conditions for pooling system voltage fluctuations to be controllable;

According to the necessary conditions for the controllable voltage fluctuation of the wind power collection system, a practical evaluation correction equation for the power transmission capacity of the wind power collection system is obtained;

The practical evaluation of the power transmission capacity of the wind power collection system is realized by using the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system.

Preferably, the voltage-reactive power sensitivity expression of the wind power collection system is:

Among them, Q _L represents the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device; E represents the external equivalent infinite bus voltage; V represents the wind farm grid-connected bus voltage; P represents the active power sent out by the wind farm; X Expressed as the equivalent reactance of the transmission line.

Preferably, the expression of the range of voltage change caused by the input of a single set of fixed capacitance compensation is:

Among them, Qc is expressed as a single set of fixed capacitance.

Preferably, the necessary conditions for the voltage fluctuation of the wind power collection system to be controllable:

Among them, ξ represents the limit value of the voltage change amplitude after inputting a single set of capacitance compensation.

Preferably, the expression of the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system is:

In order to achieve the above purpose, the present invention also provides a practical evaluation device for the power transmission capacity of the wind power collection system, the evaluation device is suitable for a dynamic reactive power compensation device, and the dynamic reactive power compensation device adopts a purely inductive branch constant reactive power control, The devices include:

The voltage-reactive power sensitivity acquisition unit is used to obtain the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch;

The necessary condition acquisition unit for controllable voltage fluctuations is used to input a single set of fixed capacitors, and obtain the range of voltage change caused by the input of a single set of fixed capacitors after compensation according to the voltage-reactive power sensitivity of the wind power collection system. The necessary condition for the controllable voltage fluctuation of the wind power collection system to obtain the voltage variation range caused by the fixed capacitor compensation;

The power transmission capacity practical evaluation correction equation acquisition unit is used to obtain the wind power collection system practical evaluation correction equation for the wind power collection system according to the necessary condition that the voltage fluctuation of the wind power collection system is controllable;

The evaluation unit is used to realize the practical evaluation of the power transmission capacity of the wind power collection system by using the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system.

Preferably, the voltage-reactive power sensitivity expression of the wind power collection system obtained by the voltage-reactive power sensitivity acquisition unit is:

Among them, Q _L represents the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device; E represents the external equivalent infinite bus voltage; V represents the wind farm grid-connected bus voltage; P represents the active power sent out by the wind farm; X Expressed as the equivalent reactance of the transmission line.

Preferably, the expression of the range of voltage change caused by the input of a single set of fixed capacitors acquired by the acquisition unit for the necessary condition for controllable voltage fluctuation is:

Among them, Qc is expressed as a single set of fixed capacitance.

Preferably, the necessary condition for controllable voltage fluctuation of the wind power collection system acquired by the acquisition unit is:

Among them, ξ represents the limit value of the voltage change amplitude after inputting a single set of capacitance compensation.

Preferably, the expression of the practical evaluation correction equation for the power transmission capacity of the wind power collection system acquired by the power transmission capacity practical evaluation correction equation acquisition unit is:

The above technical scheme has the following beneficial effects:

The practical evaluation correction equation for the power transmission capacity of the wind power collection system proposed by the present invention takes into account the influence of the control of the dynamic reactive power compensation device of the wind farm, so that the dispatching department can more accurately grasp the actual power transmission capacity of the wind power system, and avoids The overestimation of the power transmission capacity of the wind power collection system has occurred, which further ensures the safety and stability of the system.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a schematic diagram of an equivalent circuit of a traditional wind power collection system;

Fig. 2 is a flow chart of a practical evaluation method for power transmission capacity of a wind power collection system proposed by the present invention;

Fig. 3 is a block diagram of a practical evaluation device for power transmission capacity of a wind power collection system proposed by the present invention;

Fig. 4 is a comparison diagram of system voltage changes after a single set of capacitors with a capacity of 20Mvar is put into use in this embodiment.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The working principle of the present invention is: in order to avoid unnecessary power loss in daily operation in the current wind farm operation, the capacitive branch of the dynamic reactive power compensation device is usually set as manual switching, and the dynamic reactive power compensation device adopts a purely inductive branch Constant reactive power control. Therefore, the evaluation of the power transmission capacity of the wind power system with the above characteristics needs to consider the influence of the constant reactive power control of the inductive branch of the detailed dynamic reactive power compensation device. Equation 4 is the voltage-reactive power sensitivity of the system after considering the constant reactive power control of the inductive branch:

Among them, Q _L is the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device, and other parameters are still the same as those in Figure 1. Assuming that the capacity of a single set of fixed capacitors is still Qc, the range of voltage change caused by putting in a single set of fixed capacitors is:

Similarly, if the voltage change range limit is ξ after a single set of capacitor compensation is put into use, then the necessary conditions for the controllable voltage fluctuation of the system become:

Finally, the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system is deduced from Equation 6:

Observing the existing evaluation equation and correction equation of wind power transmission capacity, it can be concluded that after considering the control of dynamic reactive power compensation device and meeting the requirements of voltage fluctuation range, the estimated value of wind power transmission capacity will decrease, and the power transmission capacity of wind power system will be reduced. weaken. Thus avoiding the overestimation of the output capacity of the wind power system, which seriously threatens the stable operation of the system.

Based on the above working principle, the present invention proposes a flow chart of a practical evaluation method for the transmission capacity of a wind power collection system. Branch constant reactive power control, the method includes:

Step 201): Obtain the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch;

Step 202): Putting in a single set of fixed capacitors, according to the voltage-reactive power sensitivity of the wind power collection system, obtaining the range of voltage change caused by the input of the single set of fixed capacitors after compensation, and according to the voltage caused by the input of the single set of fixed capacitors after compensation The range of change obtains the necessary conditions for the controllable voltage fluctuation of the wind power collection system;

Step 203): According to the necessary conditions for the controllable voltage fluctuation of the wind power collection system, obtain a practical evaluation correction equation for the power transmission capacity of the wind power collection system;

Step 204): Utilizing the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system to realize the practical evaluation of the power transmission capacity of the wind power collection system.

Wherein, the expression of the voltage-reactive power sensitivity of the wind power collection system is:

In the above formula, Q _L represents the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device; E represents the external equivalent infinite bus voltage; V represents the wind farm grid-connected bus voltage; P represents the active power sent from the wind farm ; X represents the transmission reactance.

Wherein, the expression of the range of voltage change caused by the input of a single set of fixed capacitance compensation is:

In the above formula, Qc is expressed as a single set of fixed capacitance.

Among them, the necessary conditions for the voltage fluctuation of the wind power collection system to be controllable:

In the above formula, ξ represents the limit value of the voltage change amplitude after inputting a single set of capacitor compensation.

Wherein, the expression of the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system is:

As shown in FIG. 3 , it is a block diagram of a practical evaluation device for power transmission capacity of a wind power collection system proposed by the present invention. This evaluation device is suitable for dynamic reactive power compensation device, which adopts pure inductive branch constant reactive power control, and the device includes:

The voltage-reactive power sensitivity acquisition unit 301 is used to obtain the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch;

The necessary condition acquisition unit 302 for controllable voltage fluctuations is used to input a single set of fixed capacitors, and obtain the range of voltage change caused by the input of a single set of fixed capacitors after compensation according to the voltage-reactive power sensitivity of the wind power collection system. The necessary condition for obtaining the controllable voltage fluctuation of the wind power collection system is obtained from the voltage change range caused by the group fixed capacitor compensation;

The power transmission capacity practical evaluation correction equation acquisition unit 303 is used to obtain the wind power collection system practical evaluation correction equation according to the necessary conditions for the controllable voltage fluctuation of the wind power collection system;

The evaluation unit 304 is configured to implement the practical evaluation of the power transmission capacity of the wind power collection system by using the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system.

In order to understand the present invention in depth, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings and application examples.

At present, the capacity of a single group of fixed capacitors in wind farms is about 20Mvar. According to the relevant regulations of the power system, the voltage change of the busbar caused by switching of a single group of reactive power compensation devices in the system should not exceed 2.5% of the rated voltage. Taking the simple system in Fig. 1 as an example, calculate the estimated value of power transmission capacity of the system in Fig. 1 before and after the evaluation equation is revised. The specific parameters of the system are as follows: external equivalent infinite bus voltage: E = 1 (pu); wind farm grid-connected point voltage: V = 1 (pu); system reference capacity: S = 1000MVA; single group fixed capacitance compensation capacity: Q _c = 0.02(pu); the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device: Q _L =0.039(pu); the equivalent reactance of the transmission line: X=0.6(pu).

In order to satisfy that the voltage fluctuation range is less than 2.5% of the rated voltage, the wind power active output P obtained from the existing evaluation equation of the wind power collection system transmission capacity should be less than 0.83(pu), while the wind power active output P obtained by the correction equation listed in Equation 6 P should be lower than 0.76(pu). Obviously, after considering the control of the dynamic reactive power compensation device, within the normal voltage fluctuation range, the estimated value of wind power transmission capacity is significantly reduced.

In order to verify the accuracy of the correction equation, the active output P of the simple wind power system in Figure 1 is set to 0.83 (pu) and 0.76 (pu) respectively, and other parameters remain unchanged. As shown in FIG. 4 , it is a comparison chart of system voltage changes after a single set of capacitors with a capacity of 20Mvar is put into use in this embodiment. It can be concluded from Figure 4 that when the actual active power output of the wind power system is the estimated value of the existing evaluation equation, and the control of the dynamic reactive power compensation device is not considered, the voltage change range does not exceed 2.5% after a single group of capacitors with a capacity of 20Mvar is switched. , and considering the control of the dynamic reactive power compensation device, the voltage change range reaches 2.8%, which is more than 2.5%. . Obviously, the existing evaluation equations tend to overestimate the power transmission capacity of the actual system, while the revised equations are more accurate and closer to the actual operating conditions.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (2)

1. A practical evaluation method for power transmission capacity of a wind power collection system, characterized in that the evaluation method is applicable to a dynamic reactive power compensation device, and the dynamic reactive power compensation device adopts a purely inductive branch constant reactive power control, and the method includes : The voltage-reactive power sensitivity of the wind power collection system is obtained according to the pure inductive branch constant reactive power control, wherein the expression of the voltage-reactive power sensitivity of the wind power collection system is: <mrow><mfrac><mrow><mo>&amp;part;</mo><mi>V</mi></mrow><mrow><mo>&amp;part;</mo><mi>Q</mi></mrow></mfrac><mo>=</mo><mfrac><mrow><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</msup>mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></msup></msup>mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac></mrow> Among them, Q _L represents the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device; E represents the external equivalent infinite bus voltage; V represents the wind farm grid-connected bus voltage; P represents the active power sent out by the wind farm; X Expressed as the equivalent reactance of the transmission line; Put in a single set of fixed capacitors, and obtain the range of voltage change caused by the compensation of the input single set of fixed capacitors according to the voltage-reactive power sensitivity of the wind power collection system, and obtain the range of voltage changes caused by the input of a single set of fixed capacitors after compensation. Integrating the necessary conditions for the controllable voltage fluctuation of the system, wherein the expression of the voltage variation range caused by the input of a single set of fixed capacitance compensation is: <mrow><mi>&amp;Delta;</mi><mi>V</mi><mo>=</mo><mfrac><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac></mrow> Among them, Qc is expressed as a single set of fixed capacitance, Necessary conditions for the controllable voltage fluctuation of the wind power collection system: <mrow><mfrac><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac><mo>&lt;</mo><mi>&amp;xi;</mi></mrow> Among them, ξ represents the limit value of the voltage change amplitude after inputting a single set of capacitor compensation; According to the necessary condition for the controllable voltage fluctuation of the wind power collection system, a practical evaluation correction equation for the power transmission capacity of the wind power collection system is obtained, wherein the expression of the practical evaluation correction equation for the power transmission capacity of the wind power collection system is: <mrow><mi>P</mi><mo>&lt;</mo><msqrt><mfrac><mrow><mn>4</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mrow><mo>(</mo><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi><mo>)</mo></mrow><mrow><mo>(</mo><mo>(</mo><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi></mrow><mo>)</mo><mo>+</mo><msqrt><mrow><msup><mrow><mo>(</mo><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi><mo>)</mo></mrow><mn>2</mn></msup><mo>+</mo><mn>8</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup></mrow></msqrt><mo>)</mo></mrow></mrow><mrow><mn>8</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></mfrac></msqrt><mo>;</mo></mrow> The practical evaluation of the power transmission capacity of the wind power collection system is realized by using the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system. 2. A practical evaluation device for power transmission capacity of a wind power collection system, characterized in that the evaluation device is suitable for a dynamic reactive power compensation device, and the dynamic reactive power compensation device adopts a purely inductive branch constant reactive power control, and the device includes : The voltage-reactive power sensitivity acquisition unit is used to obtain the voltage-reactive power sensitivity of the wind power collection system according to the constant reactive power control of the pure inductive branch, wherein the voltage-reactive power sensitivity of the wind power collection system obtained by the voltage-reactive power sensitivity acquisition unit The expression of work sensitivity is: <mrow><mfrac><mrow><mo>&amp;part;</mo><mi>V</mi></mrow><mrow><mo>&amp;part;</mo><mi>Q</mi></mrow></mfrac><mo>=</mo><mfrac><mrow><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</msup>mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></msup></msup>mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac></mrow> Among them, Q _L represents the initial reactive power absorbed by the inductive branch of the dynamic reactive power compensation device; E represents the external equivalent infinite bus voltage; V represents the wind farm grid-connected bus voltage; P represents the active power sent out by the wind farm; X Expressed as the equivalent reactance of the transmission line; The necessary condition acquisition unit for controllable voltage fluctuations is used to input a single set of fixed capacitors, and obtain the range of voltage change caused by the input of a single set of fixed capacitors after compensation according to the voltage-reactive power sensitivity of the wind power collection system. The range of voltage change caused by fixed capacitor compensation is used to obtain the necessary conditions for controllable voltage fluctuations of the wind power collection system. The expression is: <mrow><mi>&amp;Delta;</mi><mi>V</mi><mo>=</mo><mfrac><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac></mrow> Among them, Qc is expressed as a single set of fixed capacitance, The necessary conditions for the controllable voltage fluctuations of the wind power collection system obtained by the acquisition unit are: <mrow><mfrac><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup><mo>-</mo><mn>2</mn><msub><mi>Q</mi><mi>L</mi></msub><mi>X</mi><msqrt><mrow><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><msup><mi>P</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></msqrt></mrow></mfrac><mo>&lt;</mo><mi>&amp;xi;</mi></mrow> Among them, ξ represents the limit value of the voltage change amplitude after inputting a single set of capacitor compensation; A practical evaluation correction equation acquisition unit for power transmission capacity, configured to obtain a practical evaluation correction equation for power transmission capacity of the wind power collection system according to the necessary conditions for controllable voltage fluctuations of the wind power collection system, wherein the practical evaluation correction equation acquisition unit for power transmission capacity The expression of the obtained correction equation for the practical evaluation of the power transmission capacity of the wind power collection system is: <mrow><mi>P</mi><mo>&lt;</mo><msqrt><mfrac><mrow><mn>4</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup><mo>-</mo><mrow><mo>(</mo><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi><mo>)</mo></mrow><mrow><mo>(</mo><mo>(</mo><mrow><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi></mrow><mo>)</mo><mo>+</mo><msqrt><mrow><msup><mrow><mo>(</mo><msub><mi>Q</mi><mi>c</mi></msub><mi>X</mi><mi>V</mi><mo>+</mo><mn>2</mn><msub><mi>&amp;xi;Q</mi><mi>L</mi></msub><mi>X</mi><mo>)</mo></mrow><mn>2</mn></msup><mo>+</mo><mn>8</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>E</mi><mn>2</mn></msup><msup><mi>V</mi><mn>2</mn></msup></mrow></msqrt><mo>)</mo></mrow></mrow><mrow><mn>8</mn><msup><mi>&amp;xi;</mi><mn>2</mn></msup><msup><mi>X</mi><mn>2</mn></msup></mrow></mfrac></msqrt><mo>;</mo></mrow> The evaluation unit is used to realize the practical evaluation of the power transmission capacity of the wind power collection system by using the correction equation for the practical evaluation of the power transmission capacity of the wind power collection system.