A multi-source cooperative offshore wind farm reactive voltage control method

Abstract

This invention discloses a multi-source coordinated reactive power and voltage control method for offshore wind farms, including establishing a voltage balance equation at the grid connection point of the offshore wind farm containing multiple sources, and determining the reactive power demand Q at the grid connection point of the offshore wind farm during wind speed fluctuations. re Based on the wake effect criterion for offshore wind farms and the active power model of offshore wind farms under the wake effect, the maximum reactive power output value Q of the wind farm without load shearing is obtained. wmax1 Establish a reactive power optimization model and constraints for offshore wind farms that consider load reduction capacity, and solve for the maximum reactive power output value Q of the wind farm after load reduction. wmax2 When the wind farm voltage fluctuates, according to Q re Q wmax1 Q wmax2 By prioritizing the control of wind farms, SVG (Static Var Generator), and electrochemical energy storage, reactive power support for the power system is implemented, enabling multi-source coordinated reactive power and voltage control of offshore wind farms. This enhances the coordinated control capability of multiple sources participating in wind farm voltage regulation, ensuring voltage stability at the grid connection point of offshore wind farms.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically relating to a method for reactive power and voltage control in offshore wind farms with multi-source coordination. Background Technology

[0002] Influenced by environmental, climatic, and resource conditions, my country has proposed building a new power system based on new energy sources. The continuous integration of new energy sources, such as wind and solar power, into the grid has led to a decrease in grid inertia and increased pressure on voltage and frequency regulation. In 2021, my country's newly installed offshore wind power capacity reached 16.9 GW, bringing the cumulative installed capacity to 26.39 GW, ranking first globally. With its abundant and stable resources, offshore wind power has developed rapidly in coastal areas, but voltage stability issues remain. In addition to traditional SVC and SVG reactive power compensation equipment, some offshore wind farms have adopted electrochemical energy storage equipment. As an excellent resource for peak shaving, frequency regulation, and voltage regulation, energy storage is a crucial support for the construction of the future new power system.

[0003] Wind speed fluctuations and insufficient reactive power regulation capabilities of offshore wind farms are important factors leading to unstable voltage at grid connection points. Therefore, multi-source coordinated voltage regulation control is particularly important.

[0004] For the future scenario of large-scale offshore wind farms equipped with SVG, electrochemical energy storage and other equipment, current research rarely involves multi-source collaborative support methods for voltage control of offshore wind farms involving electrochemical energy storage. Considering the economic and technical performance of different reactive power sources, it is necessary to study the timing method of reactive power regulation coordination between wind farm units, SVG and electrochemical energy storage, and to maximize the reactive power support potential of offshore wind farms in order to achieve rapid and effective support control of offshore wind farm grid connection points. Summary of the Invention

[0005] This invention provides a multi-source coordinated reactive power and voltage control method for offshore wind farms to solve the problems of insufficient reactive power support capacity and poor multi-source coordination of current offshore wind farm units.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A multi-source coordinated reactive power and voltage control method for offshore wind farms includes:

[0008] S1: Establish the voltage balance equation at the grid connection point of an offshore wind farm with multiple sources, and determine the reactive power demand Q at the grid connection point of the offshore wind farm under wind speed fluctuations. re ;

[0009] S2: Based on the wake effect criterion and the active power model of offshore wind farms under the wake effect, the maximum reactive power output value Q of the wind farm without load shearing is obtained. wmax1 ;

[0010] Establish a reactive power optimization model and constraints for an offshore wind farm that considers load reduction capacity, and solve for the maximum reactive power output value Q of the wind farm after load reduction. wmax2 ;

[0011] S3: When the wind farm voltage fluctuates, according to Q re Q wmax1 Q wmax2 The reactive power support of the power system is carried out according to the control priority of wind farm, SVG and electrochemical energy storage, so as to realize the reactive power and voltage control of offshore wind farms with multi-source coordination.

[0012] To optimize the above technical solution, the specific measures also include:

[0013] The aforementioned multi-source offshore wind farm includes a wind farm, an electrochemical energy storage system, and a reactive power compensation device;

[0014] A wind farm includes doubly-fed induction generators, collector lines, and step-up transformers;

[0015] Electrochemical energy storage systems include lithium batteries and PCS;

[0016] Reactive power compensation devices include SVG.

[0017] The voltage balance equation at the grid connection point of the offshore wind farm with multiple sources, established in step S1 above, is as follows:

[0018]

[0019] In the formula, U POI U is the voltage at the grid connection point of the offshore wind farm. on X is the voltage of the land power grid. L For the reactance of the transmission line from the offshore wind farm, P send and Q send These are the active power and reactive power at the grid connection point of the offshore wind farm, respectively.

[0020] Among them, P send and Q send They are respectively:

[0021] P send =P wind +P storage (2)

[0022] Q send =Q wind +Q SVG +Q storage (3)

[0023] In the formula, P wind P storage Q represents the active power of the wind farm and the electrochemical energy storage, respectively.wind Q SVG Q storage These represent the reactive power of wind farms, SVG, and electrochemical energy storage, respectively.

[0024] Step S1 above determines the reactive power demand Q of the offshore wind farm grid connection point under wind speed fluctuations based on the voltage balance equation of the multi-source offshore wind farm grid connection point. re Specifically:

[0025] Considering wind speed fluctuations, let the target value for grid connection point voltage control be U. ref At this time, the reactive power demand of the offshore wind farm grid connection point is:

[0026]

[0027] Step S2 above describes obtaining the maximum reactive power output value Q of the offshore wind farm without load shedding, based on the wake effect criterion and the active power model of the offshore wind farm under the wake effect. wmax1 The specific steps are as follows:

[0028] S21: Constructing criteria for judging the wake impact of offshore wind farms:

[0029] S w =[m ij ] N×N =[r ij ·d ij ] N×N (5)

[0030] In the formula, S w Here is the wind turbine location correlation matrix, s ij Let r be the correlation coefficient between wind turbine i and wind turbine j, N be the number of wind turbines in the wind farm, and r be the coefficient of the wind turbine i. ij Let d be the relative angle matrix between wind turbine i and wind turbine j. ij Let be the relative distance matrix between wind turbine i and wind turbine j;

[0031] r ij d ij They are respectively:

[0032]

[0033]

[0034] In the formula, θ ij Let θ be the relative angle between fan i and fan j, θ0 be the critical angle of fan wake influence, k0 be the proportionality coefficient, R be the radius of the fan, and x be the relative angle between fan i and fan j. i y i Let x be the position coordinate of wind turbine i. j y j Let J be the position coordinates of the wind turbine;

[0035] S22: Based on the wake effect criterion for offshore wind farms, establish an active power model for offshore wind farms under the influence of wake effects:

[0036]

[0037] In the formula, a i P is the wake influence factor. i (x i ) represents the active power of fan i, ρ represents the air density, and C represents the active power of fan i. p V is the wind energy utilization coefficient. i (x i ) represents the wind speed value flowing through fan i;

[0038] The wind speed of fan i is:

[0039]

[0040] In the formula, V0 is the input wind speed of the wind farm, and A s V represents the area of ​​the wake's influence. j V is the wind speed when the j-th fan is not affected by the wake. j,i Let be the wake velocity generated by the j-th fan at the location of the i-th fan.

[0041] Further, we obtain the reactive power output capacity of the wind farm, that is, the maximum reactive power output value Q of the wind farm without load shedding. wmax1 :

[0042]

[0043] In the formula, S wind This refers to the rated capacity of the fan.

[0044] Step S2 above describes establishing a reactive power optimization model and constraints for an offshore wind farm that considers load reduction capacity, and solving for the maximum reactive power output value Q of the wind farm after load reduction. wmax2 Specifically:

[0045] Establish a reactive power optimization model for offshore wind farms that consider load shedding capacity:

[0046]

[0047] The constraints are:

[0048]

[0049] In the formula, P i Q i Inject active power and reactive power into node i, respectively; G ij B ijThese are the corresponding elements in the system admittance matrix; U i U j and θ ij These represent the voltage magnitude and phase angle difference at nodes i and j, respectively; U i Per-unit values ​​representing system node voltages; These represent the minimum and maximum limits of the node voltage, respectively; d min and d max These are the lower and upper limits of the wind turbine load reduction rate;

[0050] Solve the reactive power optimization model of the offshore wind farm considering load reduction capacity to obtain the maximum reactive power output value Q of the wind farm under load reduction. wmax2 .

[0051] Step S2 above uses an improved gray wolf optimization algorithm to solve the reactive power optimization model of the offshore wind farm considering load reduction capacity, and obtains the maximum reactive power output value Q of the wind farm under load reduction. wmax2 .

[0052] The specific steps of the multi-source coordinated reactive power and voltage control of offshore wind farms in step S3 above are as follows:

[0053] When the voltage at a wind farm fluctuates:

[0054] S31: If Q re ≤Q wmax1 The wind farm regulates the reactive current reference value and generates Q. re The reactive power is adjusted to maintain the grid connection point voltage as the control target value U. ref ;

[0055] S32: If Q wmax1 <Q re ≤Q wmax2 The wind farm first implements load shedding control to increase reactive power output before participating in system reactive voltage control, aiming to maintain the grid connection point voltage as the control target value U. ref ;

[0056] S33: If Q wmax2 <Q re ≤Q wmax2 +Q SVG A reactive power optimization model for offshore wind farms that considers load reduction capacity is adopted to enable the wind farm to reach the maximum reactive power output state Q. wmax2 Then, the wind farm and SVG jointly participate in the system's reactive power and voltage control, with the target control value U being the voltage at the grid connection point. ref ;

[0057] S34: If Q wmax2 +Q SVG <Q re ≤Q wmax2 +QSVG +Q storage Wind farm output Q wmax2 The size of the reactive power, SVG output Q SVG The reactive power of wind farms, SVG, and electrochemical energy storage all participate in the reactive power and voltage control of the system, with the goal of maintaining the grid connection point voltage as the control target value U. ref .

[0058] If none of the judgment conditions in steps S31-S34 are met in step S3 above, it indicates that the voltage fluctuation is severe and the wind farm may enter a low voltage or high voltage ride-through state, requiring fault ride-through control or turbine tripping.

[0059] The present invention has the following beneficial effects:

[0060] This invention addresses offshore wind farms comprised of wind farms, electrochemical energy storage systems, and reactive power compensation devices. It establishes a voltage balance equation at the grid connection point of the offshore wind farm, including multiple sources, to determine the reactive power demand during voltage fluctuations. A wind farm power model based on wake influence criteria is established. When the reactive power output capacity of the wind farm is limited, a reactive power optimization model based on load shedding is further considered to improve the reactive power output capacity of the wind farm. Based on the actual reactive power demand at the wind farm's grid connection point, system reactive power support is implemented according to the control priorities of the wind farm, SVG (Static Var Generator), and electrochemical energy storage, maximizing the utilization of the wind farm's own reactive power capacity. Combined with the excellent reactive power control characteristics of SVG and electrochemical energy storage, the collaborative control capability of multiple sources participating in wind farm voltage regulation is enhanced, ensuring voltage stability at the offshore wind farm's grid connection point.

[0061] This invention improves the reactive power output capability of wind farms by establishing a wind farm power model based on wake influence criteria and adopting a wind farm reactive power optimization model based on load reduction. Under the premise of prioritizing the reactive power regulation capability of wind turbine units themselves, the system reactive power support is carried out according to the control priority of wind farm, SVG and electrochemical energy storage, maximizing the utilization of the reactive power capability of wind farms themselves. Combined with the excellent reactive power control characteristics of SVG and electrochemical energy storage, the collaborative control capability of multi-source participation in wind farm voltage regulation is improved, which can ensure the voltage stability of offshore wind farm grid connection points. Attached Figure Description

[0062] Figure 1 This is a flowchart of a multi-source coordinated reactive power and voltage control method for offshore wind farms.

[0063] Figure 2 This is a topology diagram of an offshore wind farm grid connection system.

[0064] Figure 3 This is a schematic diagram showing the wake effects of two wind turbine units.

[0065] Figure 4This is the active-reactive power operation diagram for a doubly-fed offshore wind turbine. Detailed Implementation

[0066] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0067] like Figure 1 As shown, a multi-source coordinated reactive power and voltage control method for offshore wind farms includes the following steps:

[0068] S1: Establish the voltage balance equation at the grid connection point of an offshore wind farm with multiple sources, and determine the reactive power demand Q at the grid connection point of the offshore wind farm under wind speed fluctuations. re ;

[0069] Grid-connected systems for offshore wind farms with multiple sources, such as Figure 2 As shown, it includes a wind farm, an electrochemical energy storage system, and a reactive power compensation device. The wind farm includes doubly fed wind turbines, collector lines, step-up transformers, etc. The electrochemical energy storage system includes lithium batteries and PCS (Power Conversion System), and the reactive power compensation device includes SVG (Static Var Compensator), etc.

[0070] S2: Based on the wake effect criterion and the active power model of offshore wind farms under the wake effect, the maximum reactive power output value Q of the wind farm without load shearing is obtained. wmax1 ;

[0071] Establish a reactive power optimization model and constraints for an offshore wind farm that considers load reduction capacity, and solve for the maximum reactive power output value Q of the wind farm after load reduction. wmax2 ;

[0072] Specifically, considering factors such as actual wind speed and wind farm layout, a wind farm power model based on wake influence criteria is established. Furthermore, a wind farm reactive power optimization model based on load reduction is adopted to determine the maximum reactive power support capacity of the wind farm after load reduction.

[0073] S3: When the wind farm voltage fluctuates, according to Q re Q wmax1 Q wmax2 The reactive power support of the power system is carried out according to the control priority of wind farm, SVG and electrochemical energy storage, so as to realize the reactive power and voltage control of offshore wind farms with multi-source coordination.

[0074] Based on steps S1 and S2, according to the actual reactive power demand of the wind farm grid connection point, the system reactive power support is carried out according to the control priority of wind farm, SVG and electrochemical energy storage, and multi-source coordinated offshore wind farm reactive power and voltage control is carried out.

[0075] In this embodiment, step S1 involves establishing the voltage equation at the grid connection point of an offshore wind farm with multiple sources:

[0076]

[0077] In the formula, U POI U is the voltage at the grid connection point of the offshore wind farm. on X is the voltage of the land power grid. L For the reactance of the transmission line from the offshore wind farm, P send and Q send These represent the active power and reactive power at the grid connection point of the offshore wind farm, respectively.

[0078] Simultaneously, establish the active and reactive power equations at the grid connection point of the offshore wind farm:

[0079] P send =P wind +P storage (2)

[0080] Q send =Q wind +Q SVG +Q storage +Q ca (3)

[0081] In the formula, P wind P storage Q represents the active power of the wind farm and the electrochemical energy storage, respectively. wind Q SVG Q storage These represent the reactive power of wind farms, SVG, and electrochemical energy storage, respectively.

[0082] Considering wind speed fluctuations, let the target value for grid connection point voltage control be U. ref At this time, the reactive power demand of the offshore wind farm grid connection point is:

[0083]

[0084] In this embodiment, step S2 is specifically performed as follows:

[0085] S21: A schematic diagram of the wake effect formed by two generator units is shown below. Figure 3 As shown, the criteria for determining the wake impact of offshore wind farms are constructed as follows:

[0086] S w =[m ij ] N×N =[r ij ·d ij ] N×N (5)

[0087] In the formula, S w Here is the wind turbine location correlation matrix, s ij Let r be the correlation coefficient between wind turbine i and wind turbine j, N be the number of wind turbines in the wind farm, and r be the coefficient of the wind turbine i. ijLet d be the relative angle matrix between wind turbine i and wind turbine j. ij Let be the relative distance matrix between wind turbine i and wind turbine j.

[0088] The relative angle matrix and relative distance matrix between wind turbine i and wind turbine j are as follows:

[0089]

[0090]

[0091] In the formula, θ ij Let θ be the relative angle between fan i and fan j, θ0 be the critical angle of fan wake influence (taken as 15° here), k0 be the proportionality coefficient (taken as 15), and R be the radius of the fan. i y i Let x be the position coordinate of wind turbine i. j y j Let J be the position coordinates of wind turbine j. S22: Based on the wake effect criterion for offshore wind farms, establish the active power equation for offshore wind farms under the influence of wake effects:

[0092]

[0093] In the formula, a i P is the wake influence factor. i (x i ) represents the active power of fan i, ρ represents the air density, and C represents the active power of fan i. p V is the wind energy utilization coefficient. i (x i ) represents the wind speed value flowing through fan i.

[0094] The wind speed of fan i is:

[0095]

[0096] In the formula, V0 is the input wind speed of the wind farm, and A s V represents the area of ​​the wake's influence. j V is the wind speed when the j-th fan is not affected by the wake. j,i Let m be the wake velocity generated by the j-th fan at the location of the i-th fan. ij A value of 0 indicates that there is no wake effect between the fans, while a value of 1 indicates that there is a wake effect between the fans.

[0097] Offshore wind farms use doubly-fed induction generators (DFIGs), and their active and reactive power operating ranges are as follows: Figure 4 As shown.

[0098] Only after determining the active power value of each wind turbine in the wind farm can the reactive power value of each wind turbine be further solved or optimized, that is, the reactive power output capacity of the wind farm can be further obtained based on formulas (5)-(9):

[0099]

[0100] In the formula, S wind This refers to the rated capacity of the fan.

[0101] If the wind farm cannot meet the reactive power demand of the grid connection point, a load shedding operation needs to be performed on the wind farm. In this case, the reactive power output capacity of the wind farm is:

[0102]

[0103] In the formula, d i is the load reduction factor for wind turbine unit i.

[0104] S23: Establish a reactive power optimization model for offshore wind farms that consider load shedding capacity:

[0105]

[0106] The constraints are:

[0107]

[0108] In the formula, P i Q i Inject active power and reactive power into node i, respectively; G ij B ij These are the corresponding elements in the system admittance matrix; U i U j and θ ij These represent the voltage magnitude and phase angle difference at nodes i and j, respectively; U i Per-unit values ​​representing system node voltages; These represent the minimum and maximum limits of the node voltage, respectively; d min and d max These are the lower and upper limits of the wind turbine load reduction rate.

[0109] An improved gray wolf optimization algorithm was used to solve the model, and the maximum reactive power output value Q of the wind farm after load reduction was obtained. wmax2 .

[0110] In this embodiment, the multi-source coordinated reactive power and voltage control method for offshore wind farms described in step S3 follows the process as follows: Figure 1 As shown, the specific steps are as follows:

[0111] Based on the reactive power demand Q of the wind farm determined in step S1 re The maximum reactive power output value Q of the wind farm before load shedding, determined in step S2. wmax1 The maximum reactive power output value Q of the wind farm without load shedding wmax2 When the voltage of a wind farm fluctuates:

[0112] S31: If Q re ≤Q wmax1 The wind farm regulates the reactive current reference value and generates Q. re The magnitude of reactive power;

[0113] S32: If Q wmax1 <Q re ≤Q wmax2 The wind farm first implements load reduction control to increase reactive power output capacity before participating in system reactive voltage control.

[0114] S33: If Q wmax2 <Q re ≤Q wmax2 +Q SVG A reactive power optimization model for offshore wind farms that considers load reduction capacity is adopted to enable the wind farm to reach the maximum reactive power output state Q. wmax2 Then the wind farm and SVG jointly participate in the system's reactive power and voltage control;

[0115] S34: If Q wmax2 +Q SVG <Q re ≤Q wmax2 +Q SVG +Q storage Wind farm output Q wmax2 The size of the reactive power, SVG output Q SVG The reactive power of wind farms, SVG, and electrochemical energy storage all participate in the reactive voltage control of the system.

[0116] If none of the discrimination conditions in steps S31-S34 are met, it indicates that the voltage fluctuation is severe and the wind farm may enter a low voltage or high voltage ride-through state, requiring fault ride-through control or turbine tripping.

[0117] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for reactive power and voltage control in a multi-source coordinated offshore wind farm, characterized in that, include: S1: Establish the voltage balance equation at the grid connection point of the offshore wind farm with multiple sources, and determine the reactive power demand at the grid connection point of the offshore wind farm under wind speed fluctuations. Q re ; The voltage balance equations for the grid connection point of a multi-source offshore wind farm are established as follows: （1） In the formula, U POI This refers to the voltage at the grid connection point of the offshore wind farm. U on The voltage of the land power grid. X L Reactance for power transmission lines to offshore wind farms. P send and Q send These are the active power and reactive power at the grid connection point of the offshore wind farm, respectively. in, P send and Q send They are respectively: （2） （3） In the formula, P wind , P storage These represent the active power of the wind farm and the electrochemical energy storage, respectively. Q wind , Q SVG , Q storage These represent the reactive power of wind farms, SVG, and electrochemical energy storage, respectively. S2: Based on the wake effect criterion for offshore wind farms and the active power model of offshore wind farms under the wake effect, the maximum reactive power output value of the wind farm without load shearing is obtained. Q wmax1 ; Establish a reactive power optimization model and constraints for offshore wind farms that consider load reduction capabilities, and solve for the maximum reactive power output value of the wind farm after load reduction. Q wmax2 ; S3: When the voltage of the wind farm fluctuates, according to Q re , Q wmax1 , Q wmax2 The reactive power support of the power system is carried out according to the control priority of wind farm, SVG and electrochemical energy storage, so as to realize the reactive power and voltage control of offshore wind farms with multi-source coordination.

2. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 1, characterized in that, The multi-source offshore wind farm includes a wind farm, an electrochemical energy storage system, and a reactive power compensation device. A wind farm includes doubly-fed induction generators, collector lines, and step-up transformers; Electrochemical energy storage systems include lithium batteries and PCS; Reactive power compensation devices include SVG.

3. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 1, characterized in that, Step S1 determines the reactive power demand at the grid connection point of the offshore wind farm under wind speed fluctuations based on the voltage balance equation at the grid connection point of the offshore wind farm containing multiple sources. Q re Specifically: Considering wind speed fluctuations, let the target voltage control value at the grid connection point be... U ref At this time, the reactive power demand of the offshore wind farm grid connection point is: （4）。 4. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 1, characterized in that, Step S2 describes obtaining the maximum reactive power output value of the offshore wind farm without load shedding, based on the wake effect criterion and the active power model of the offshore wind farm under the wake effect. Q wmax1 The specific steps are as follows: S21: Constructing criteria for judging the wake impact of offshore wind farms: （5） In the formula, S w This is the wind turbine location correlation matrix. m ij For wind turbine i Japanese-style fan j The correlation coefficient, N This represents the number of wind turbines in the wind farm. r ij For wind turbine i With wind turbine j The relative angle matrix, d ij For wind turbine i With wind turbine j The relative distance matrix; r ij , d ij They are respectively: （6） （7） In the formula, θ ij For wind turbine i With wind turbine j The relative angle, m ij For wind turbine i With wind turbine j The relative distance, θ 0 is the critical angle for the influence of the fan wake. k 0 represents the proportionality coefficient. R Where is the radius of the wind turbine. x i , y i For wind turbine i Location coordinates, x j , y j For wind turbine j Position coordinates; S22: Based on the wake effect criterion for offshore wind farms, establish an active power model for offshore wind farms under the influence of wake effects: （8） In the formula, a i For wind turbine i The wake influence factor, P i ( a i (for fans) i active power, ρ air density, C p The wind energy utilization coefficient, V i ( x i ) is flowing through the fan i The wind speed value; Fan i The wind speed is: （9） In the formula, V 0 represents the input wind speed of the wind farm. A s The area affected by the wake. V j For the first j Wind speed when the typhoon is unaffected by the wake. V j,i For the first j Typhoon machine in i The wake velocity generated by the location of the typhoon generator; Maximum reactive power output of wind farm without load shedding Q wmax1 : （10） In the formula, S wind This refers to the rated capacity of the fan.

5. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 4, characterized in that, Step S2 involves establishing a reactive power optimization model and constraints for an offshore wind farm that considers load reduction capacity, and solving for the maximum reactive power output value of the wind farm after load reduction. Q wmax2 Specifically: Establish a reactive power optimization model for offshore wind farms that consider load shedding capacity: （12） In the formula, d i For wind turbines i The load reduction factor; The constraints are: （13） In the formula, P i , Q i They are nodes i Injecting active and reactive power; G ij , B ij These are the corresponding elements in the system admittance matrix; U i , U j and θ ij They are nodes i and j The voltage amplitude and phase angle difference; U i Per-unit values ​​representing system node voltages; , These represent the minimum and maximum limits for node voltage, respectively. d min and d max These are the lower and upper limits of the wind turbine load reduction rate; Solve the reactive power optimization model of the offshore wind farm considering load reduction capacity to obtain the maximum reactive power output value of the wind farm under load reduction. Q wmax2 .

6. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 5, characterized in that, Step S2 uses an improved gray wolf optimization algorithm to solve the reactive power optimization model of the offshore wind farm considering load reduction capacity, and obtains the maximum reactive power output value of the wind farm under load reduction. Q wmax2 .

7. The method for reactive power and voltage control in a multi-source coordinated offshore wind farm according to claim 1, characterized in that, The specific steps of multi-source coordinated reactive power and voltage control in offshore wind farms in step S3 are as follows: When the voltage at a wind farm fluctuates: S31: If Q re ≤ Q wmax1 Reference value for reactive current regulation in wind farms, issued Q re The amount of reactive power is determined to maintain the grid connection point voltage as the control target. U ref ; S32: If Q wmax1 < Q re ≤ Q wmax2 The wind farm first implements load shedding control to increase reactive power output before participating in system reactive voltage control, with the goal of maintaining the grid connection point voltage. U ref ; S33: If Q wmax2 < Q re ≤ Q wmax2 + Q SVG A reactive power optimization model for offshore wind farms that considers load reduction capacity is adopted to enable the wind farms to reach the maximum reactive power output state. Q wmax2 Then, the wind farm and SVG jointly participate in the system's reactive power and voltage control, with the goal of maintaining the grid connection point voltage. U ref ; S34: If Q wmax2 + Q SVG < Q re ≤ Q wmax2 + Q SVG + Q storage Wind farm output Q wmax2 Reactive power of varying magnitude, SVG output Q SVG The reactive power of wind farms, SVG, and electrochemical energy storage all participate in the reactive power and voltage control of the system, with the goal of maintaining the grid connection point voltage. U ref .

8. A multi-source coordinated reactive power and voltage control method for offshore wind farms according to claim 7, characterized in that, In step S3, if none of the judgment conditions in steps S31-S34 are met, it indicates that the voltage fluctuation is severe and the wind farm may enter a low voltage or high voltage ride-through state, requiring fault ride-through control or turbine tripping.

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