A reactive power support method for wind farms considering active power curtailment

Abstract

The present invention discloses a wind farm reactive power support method considering active power reduction in the field of wind farm reactive power support technology, comprising the following steps: Step 1, calculating the active power reduction priority coefficient c of each wind turbine; k ; Step 2, SCADA system detects the voltage at the grid connection point. If the voltage exceeds the limit, the AVC system sends a reactive power instruction ΔQ to the wind farm; Step 3, if ΔQ1

Description

Technical Field

[0001] The present invention belongs to the technical field of reactive power support for wind farms, and in particular relates to a reactive power support method for wind farms taking active power reduction into consideration. Background Art

[0002] The global fossil energy crisis has made the demand for new energy increasingly urgent, and wind power, as a clean energy source, is becoming increasingly popular. However, as the proportion of wind power installed capacity in the power grid increases, the impact of wind power generation on the power grid is increasing, and voltage stability has become an important factor affecting the grid connection of wind farms.

[0003] To maintain voltage stability at the grid connection point of a wind farm, reactive power compensation devices are typically installed, requiring a large amount of reactive power to support the grid connection point voltage. In reality, wind farms inherently possess a certain degree of reactive power voltage regulation capability. This capability can be leveraged to provide reactive power support when a reactive power shortage occurs in the grid, and to provide emergency reactive power control when necessary. Therefore, the rational development and research of reactive power voltage control methods for wind farms is crucial.

[0004] At present, existing research on reactive power and voltage control methods for wind farms mainly focuses on the coordinated control of external reactive power compensation devices and the reactive power and voltage control of the wind farm itself. There is almost no attention paid to the differences in reactive power adequacy among wind farms, and there are few control schemes or utilization methods when the reactive power adequacy of relevant wind farms is insufficient. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a reactive power support method for a wind farm taking active power reduction into consideration, so as to solve the problems raised in the above background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for reactive power support of a wind farm considering active power reduction comprises the following steps:

[0008] Step 1: Detect the active power of wind turbines in the wind farm, consider the wake effect between wind turbines, and calculate the active power reduction priority coefficient c of each wind turbine. k ;

[0009] Step 2: The SCADA system detects the voltage at the grid connection point. If the voltage exceeds the limit, the AVC system issues a reactive power command ΔQ to the wind farm.

[0010] Step 3: The reactive power compensation device SVG configured in the wind farm generates reactive power ΔQ1 according to the reactive power command. If ΔQ1 < ΔQ and the grid connection point voltage still exceeds the limit, then proceed to step 4. Otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0011] Step 4: If the wind turbines in the wind farm cannot meet the system reactive power demand, the wind turbines in the wind farm continue to generate reactive power ΔQ2. If ΔQ1+ΔQ2<ΔQ and the grid connection point voltage still exceeds the limit, proceed to step 5. Otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0012] Step 5: If the wind turbine and its equipped reactive power compensation device cannot meet the reactive power demand of the system, the wind turbine reduces its active power according to the active power reduction priority coefficient calculated in step 1, and increases its reactive power capacity ΔQ3 by reducing its active power.

[0013] Step 6: If ΔQ1+ΔQ2+ΔQ3<ΔQ and the grid connection point voltage still exceeds the limit, return to step 5; otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0014] Preferably, the method for determining the priority of active power reduction of wind turbines in step 1 is as follows:

[0015] When the reactive capacity of the wind farm is exhausted, calculate the active power P generated by the wind farm. f and reactive Q f ;

[0016] The kth wind turbine reduces its active power ΔP D , calculate the active power P of the wind turbine affected by the wake effect m (The active power of the mth wind turbine affected by the wake effect) and the active power of the wind turbine not affected by the wake effect P n (The nth wind turbine is not affected by the wake effect), calculate the total active power P of the wind farm all =∑P m +∑P n +(P k -ΔP D ),(m,n≠k);

[0017] According to the active power of each wind turbine, the reactive power of each wind turbine is obtained, and the total reactive power of the wind farm is calculated.

[0018] Calculate the active power reduction priority coefficient of the kth wind turbine C k The smaller it is, the higher the priority of active power reduction of the wind turbine, and vice versa.

[0019] Beneficial effects of the present invention:

[0020] 1. The method of the present invention achieves coordinated distribution of reactive capacity among wind turbines by reducing active power, thus avoiding the problem of some wind turbines in a wind farm having their reactive capacity exhausted while others still have a large reactive power margin. Furthermore, when a reactive power shortage occurs in the system, the wind farm can provide reactive power support for the system by reducing the minimum active power.

[0021] 2. The method of the present invention takes into account the wake effect between wind turbines, so that the wind farm is more in line with the actual situation when adjusting the active and reactive power. In addition, when the reactive capacity of the wind farm is insufficient, it can still reduce the active power reduction of the wind farm as much as possible while ensuring the reactive power demand of the power system, thereby improving the wind energy absorption capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0024] Figure 2 is a graph showing the rotational speed and wind speed of the fan in an embodiment of the present invention;

[0025] Figure 3 is a graph showing the power and wind speed of a fan in an embodiment of the present invention;

[0026] Figure 4 This is a system wiring diagram in an embodiment of the present invention;

[0027] Figure 5 This is a simplified wiring diagram of the system in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] See also Figure 1 As shown, this embodiment provides a method for reactive power support of a wind farm taking active power reduction into consideration, including the following steps:

[0030] Step 1: Detect the active power of wind turbines in the wind farm, consider the wake effect between wind turbines, and calculate the active power reduction priority coefficient c of each wind turbine. k ;

[0031] Among them, considering the wake effect of the wind turbine, the input wind speed of the wind turbine is v0, and the back wind speed is v w0 as follows:

[0032]

[0033] Where, c p-th is the theoretical power coefficient of the fan, which indicates the proportion of the maximum power absorbed by the fan from the airflow;

[0034] When considering the input wind speed of any wind turbine in a wind farm, it is necessary to consider the interaction between different wind turbines in the wind farm and the random variation of wind speed. The wind speed acting on any wind turbine is as follows:

[0035]

[0036] Where, v j is the wind speed acting on any unit; v w-k is the wake velocity of the kth wind turbine acting on the jth wind turbine when considering the wake effect between wind turbines, v j0 is the wind speed on the jth wind turbine without any influence; β k is the wake effect coefficient of the kth wind turbine acting on the jth wind turbine.

[0037] Considering the wake effect between wind turbines, the method for determining the priority of wind turbine active power reduction is as follows:

[0038] 1.1. When the reactive capacity of the wind farm is exhausted, calculate the active power P generated by the wind farm f and reactive Q f ;

[0039] 1.2. Active power reduction of the kth wind turbine ΔP D , calculate the active power P of the wind turbine affected by the wake effect m (The active power of the mth wind turbine affected by the wake effect) and the active power of the wind turbine not affected by the wake effect P n (The nth wind turbine is not affected by the wake effect), calculate the total active power P of the wind farm all =∑P m +∑P n +(P k -ΔP D ),(m,n≠k);

[0040] 1.3. Calculate the reactive power of each wind turbine based on the active power of each wind turbine and calculate the total reactive power of the wind farm

[0041] 1.4. Calculate the active power reduction priority coefficient of the kth wind turbine C k The smaller it is, the higher the priority of active power reduction of the wind turbine, and vice versa.

[0042] Step 2: The SCADA system detects the voltage at the grid connection point. If the voltage exceeds the limit, the AVC system issues a reactive power command ΔQ to the wind farm.

[0043] Step 3: The reactive power compensation device SVG configured in the wind farm generates reactive power ΔQ1 according to the reactive power command. If ΔQ1 < ΔQ and the grid connection point voltage still exceeds the limit, then proceed to step 4. Otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0044] Step 4: If the wind turbines in the wind farm cannot meet the system reactive power demand, the wind turbines in the wind farm continue to generate reactive power ΔQ2. If ΔQ1+ΔQ2<ΔQ and the grid connection point voltage still exceeds the limit, proceed to step 5. Otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0045] Step 5: If the wind turbine and its equipped reactive power compensation device cannot meet the reactive power demand of the system, the wind turbine reduces its active power according to the active power reduction priority coefficient calculated in step 1, and increases its reactive power capacity ΔQ3 by reducing its active power.

[0046] Among them, the apparent power of the i-th fan is S i , the power emitted is P i , the active power reduction is ΔP i , then the i-th wind turbine provides reactive power ΔQ by reducing active power i as follows:

[0047]

[0048] Active power reduction adopts a priority ranking method to sort the wind turbines' active power reduction priorities. Prioritizing reduction will release the wind turbines with the smallest active power reduction under the same reactive power conditions, thus achieving reactive power support for the system. The conditions that the wind farm needs to meet are as follows:

[0049]

[0050]

[0051] Where ΔP is the active power reduction of the wind farm. While meeting the reactive power demand of the system, the wind farm must also minimize the total active power reduction.

[0052] Step 6: If ΔQ1+ΔQ2+ΔQ3<ΔQ and the grid connection point voltage still exceeds the limit, return to step 5; otherwise, the wind farm can provide sufficient reactive power support and the step ends.

[0053] In this application embodiment, the wind farm is a direct-drive wind turbine with a wind turbine capacity of 1.5MW and a rotor radius of 37.5m. The wind turbine speed and power change with wind speed as shown in the table below. Figure 2 , as shown in 3. Figure 4The wind farm shown consists of nine 0.5 MW direct-drive wind turbines, each spaced 330 meters apart and connected to the grid via the wind farm's main transformer. A system reactive power deficit of 0.45 MW is detected, indicating insufficient reactive capacity. The wind speed blowing toward the wind farm is constant at 11 m / s, with a wind direction angle of α. This results in a shading coefficient of 0.3 between the first and second rows of wind turbines, and a shading coefficient of 0.3 between the second and third rows of wind turbines. There is no shading between the first and third rows of wind turbines, so the shading coefficient between the first and second rows is 0. The wind turbines in each row are independent of each other.

[0054] The reactive capacity of the wind farm is insufficient, and it is necessary to increase the reactive capacity by reducing the active power. The working state of each column of wind turbines is the same, so they are equivalent to Figure 5 At this time, the input wind speed, active power output and reactive power capacity of each wind turbine in the wind farm are shown in Table 1:

[0055] Table 1

[0056] WT1 WT2 WT3 Input wind speed (m / s) 11.00 10.00 9.71 Active power output (MW) 1.4994 1.2613 1.1830 Reactive capacity (MVar) 0.041 0.811 0.922

[0057] Reduce the active power of each wind turbine by 0.15MW and calculate the active power reduction priority coefficient C of the wind turbine. k .

[0058] Calculate the active power reduction priority coefficient c1 of the first wind turbine. When the active power of the first wind turbine is reduced by 0.15MW, the input wind speed, active power output and reactive power capacity of each wind turbine are shown in Table 2:

[0059] Table 2

[0060] WT1 WT2 WT3 Input wind speed (m / s) 11.00 10.1396 9.7460 Active power output (MW) 1.3494 1.2955 1.1928 Reactive capacity (MVar) 0.6550 0.7561 0.9095

[0061] According to the formula Calculation shows c1 = 0.1944.

[0062] Calculate the active power reduction priority coefficient c1 of the second wind turbine. When the second wind turbine reduces its active power by 0.15MW, the input wind speed, active power output, and reactive power capacity of each wind turbine are shown in Table 3:

[0063] Table 3

[0064] WT1 WT2 WT3 Input wind speed (m / s) 11.00 10.1396 9.8860 Active power output (MW) 1.4994 1.1113 1.2299 Reactive capacity (MVar) 0.041 1.0075 0.8586

[0065] According to the formula Calculated c2 = 0.7807.

[0066] Calculate the active power reduction priority coefficient c1 of the third wind turbine. When the third wind turbine reduces its active power by 0.15MW, the input wind speed, active power output, and reactive power capacity of each wind turbine are shown in Table 4:

[0067] Table 4

[0068] WT1 WT2 WT3 Input wind speed (m / s) 11.00 10.00 9.71 Active power output (MW) 1.4994 1.2613 1.0330 Reactive capacity (MVar) 0.041 0.811 1.0876

[0069] According to the formula Calculation shows c3 = 0.9069.

[0070] The calculation results show that the wind turbines in column 1 have the lowest active power reduction priority coefficient, 0.1944, so the active power of the wind turbines in column 1 is reduced first. When the active power of each wind turbine in column 1 is reduced by 0.033 MW, the wind farm's increased reactive capacity is 0.453 MW, which can now meet the system's reactive power shortage.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for reactive power support of a wind farm considering active power reduction, characterized in that: The following steps are involved: Step 1: Detect the active power of wind turbines in the wind farm, consider the wake effect between wind turbines, and calculate the active power reduction priority coefficient of each wind turbine. ; Step 2: The SCADA system detects the voltage at the grid connection point. If the voltage exceeds the limit, the AVC system issues a reactive power command to the wind farm. ; Step 3: The reactive power compensation device SVG configured in the wind farm sends reactive power according to the reactive power instruction. ,like < If the grid connection point voltage still exceeds the limit, proceed to step 4. Otherwise, the wind farm can provide sufficient reactive power support and the step ends. Step 4: If the wind turbines in the wind farm cannot meet the reactive power demand of the system, the wind turbines in the wind farm will continue to generate reactive power. ,like < If the grid connection point voltage still exceeds the limit, proceed to step 5. Otherwise, the wind farm can provide sufficient reactive power support and the steps are terminated. Step 5: If the wind turbine and its equipped reactive power compensation device cannot meet the reactive power demand of the system, the wind turbine will reduce its active power according to the active power reduction priority coefficient calculated in step 1, and increase its reactive power capacity by reducing its active power. ; Step 6: If < If the grid connection point voltage still exceeds the limit, return to step 5; otherwise, the wind farm can provide sufficient reactive power support and the step ends; The method for determining the priority of active power reduction of the wind turbine in step 1 is as follows: When the reactive capacity of the wind farm is exhausted, calculate the active capacity generated by the wind farm. and reactive power ; No. Typhoon turbines reduce active power , calculate the active power of the wind turbine affected by the wake effect (No. Active power of wind turbines affected by wake effect and active power of wind turbines not affected by wake effect (No. wind turbines without wake effect), calculate the total active power of the wind farm ; According to the active power of each wind turbine, the reactive power of each wind turbine is obtained, and the total reactive power of the wind farm is calculated. ; Calculate the Active power reduction priority coefficient of typhoon generators , The smaller it is, the higher the priority of active power reduction of the wind turbine, and vice versa.

2. A method for reactive power support of a wind farm considering active power reduction according to claim 1, characterized in that: In step 1, the wake effect of the fan is considered, and the input wind speed of the fan is , back wind speed as follows: Where, , is the theoretical power coefficient of the fan, which indicates the proportion of the maximum power absorbed by the fan from the airflow; When considering the input wind speed of any wind turbine in a wind farm, it is necessary to consider the interaction between different wind turbines in the wind farm and the random variation of wind speed. The wind speed acting on any wind turbine is as follows: Where, is the wind speed acting on any unit; To consider the wake effect between units The typhoon acts on The wake wind speed on the typhoon, For the first Wind speed on the typhoon machine; For the The typhoon acts on Wake effect coefficient on typhoon turbine.

3. The method for reactive power support of a wind farm considering active power reduction according to claim 1, characterized in that: In step 5 The apparent power of the typhoon is , the power emitted is , the active power reduction is , then Typhoon generators reduce the reactive power provided by active power as follows: Active power reduction adopts a priority ranking method to sort the wind turbines' active power reduction priorities. Prioritizing reduction will release the wind turbines with the smallest active power reduction under the same reactive power conditions, thus achieving reactive power support for the system. The conditions that the wind farm needs to meet are as follows: Where, The wind farm must minimize the total active power reduction while meeting the reactive power demand of the system.

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