Reactive Power Configuration Method, Device, Equipment and Storage Medium for Offshore Wind Farm

Abstract

The present invention discloses a reactive power configuration method, device, equipment and storage medium for an offshore wind farm. The method includes: constructing a two-layer planning model for reactive power configuration of the offshore wind farm, where the model includes an upper-layer configuration model and a lower-layer operation model; making the upper-layer configuration model aim at minimizing the annual investment cost of reactive power compensation devices, with dynamic voltage security constraints and the minimum compensation capacity constraints of the offshore wind farm as the constraint conditions, determining the initial reactive power configuration capacity, and correspondingly transmitting it to the lower-layer operation model; making the lower-layer operation model calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and correspondingly returning it to the upper-layer configuration model; making the upper-layer configuration model calculate the optimal reactive power configuration capacity according to the minimum annual investment cost of reactive power compensation devices and the annual operation cost of the offshore wind farm. The above method is based on the configuration and operation requirements of the offshore wind farm, utilizes the reactive power regulation ability of wind turbines to reduce the reactive power compensation capacity, and improves the economic efficiency through the minimum annual comprehensive cost.

Description

Technical Field

[0001] The present invention relates to the technical field of reactive power optimization in wind farms, and particularly to a reactive power configuration method, device, equipment and storage medium for an offshore wind farm. Background Art

[0002] In the past decade, benefited from technological progress, cost reduction and policy support, the installed capacity of offshore wind power has increased exponentially. With the increase of the offshore wind power penetration rate, its reactive power and voltage problems have become increasingly prominent, because the randomness of wind power and the charging power of high-voltage AC submarine cables pose challenges to the reactive power compensation of offshore wind farms, and technicians need to reasonably configure the reactive power of offshore wind farms to meet the operation requirements and economic benefits.

[0003] At present, permanent magnet synchronous wind turbines with full-power converters are widely used in offshore wind farms. Permanent magnet synchronous wind turbines have flexible reactive power regulation capabilities and can cooperate with reactive power compensation devices to meet the dynamic reactive power requirements of wind farms. Among them, the reactive power compensation devices for offshore wind farms include static reactive power compensation devices and dynamic reactive power compensation devices. Generally, a high-voltage shunt reactor (HVSR) is selected as the static reactive power compensation device to compensate for part of the capacitive reactive power of the submarine cable, and a static synchronous compensator (STATCOM) is selected as the dynamic reactive power compensation device to suppress the reactive power fluctuations caused by the randomness of wind energy. However, how to optimize the capacities of the static compensation device and the dynamic compensation device, and how to coordinately distribute the reactive power output of the dynamic reactive power sources are the key points and difficulties of the current reactive power configuration problem in offshore wind farms.

[0004] The existing research on reactive power configuration in offshore wind farms mainly uses static optimization methods to determine the reactive power compensation capacity. However, the static optimization method is at the minute-level time scale, while the dynamic is at the second-level time scale, which makes the static optimization method unable to ensure transient and dynamic voltage stability, and the reactive power compensation configuration scheme determined based on the static optimization method is also difficult to reflect the operation economy of offshore wind farms. Summary of the Invention

[0005] The purpose of the present invention is to at least solve one of the technical problems existing in the prior art, and provide a reactive power configuration method, device, equipment and storage medium for an offshore wind farm. Among them, the reactive power configuration method for the offshore wind farm reduces the reactive power compensation capacity by considering the requirements of both the configuration and operation levels of the offshore wind farm, and improves the economic benefits of the offshore wind farm by minimizing the annual comprehensive cost.

[0006] In a first aspect, the present invention provides a reactive power configuration method for an offshore wind farm, including:

[0007] Construct a two - layer planning model for reactive power configuration of an offshore wind farm. The model includes an upper - layer configuration model and a lower - layer operation model;

[0008] Let the upper - layer configuration model aim at minimizing the annual investment cost of reactive power compensation devices, with dynamic voltage security constraints and the minimum compensation capacity constraints of the offshore wind farm as constraints, determine the initial reactive power configuration capacity, and transfer the initial reactive power configuration capacity to the lower - layer operation model;

[0009] Let the lower - layer operation model calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and return the minimum annual operation cost of the offshore wind farm to the upper - layer configuration model;

[0010] Let the upper - layer configuration model calculate the optimal reactive power configuration capacity of the offshore wind farm according to the minimum annual investment cost of reactive power compensation devices and the received minimum annual operation cost of the offshore wind farm.

[0011] As a further improvement, the dynamic voltage security constraints are determined according to the voltage adaptability requirements, steady - state voltage requirements, and low - voltage ride - through operation requirements under the grid - connection standard of the offshore wind farm; the minimum compensation capacity constraints of the offshore wind farm are determined according to the maximum reactive power compensation demand after considering the reactive power regulation ability of wind turbines in the offshore wind farm.

[0012] As a further improvement, the maximum reactive power compensation demand after considering the reactive power regulation ability of wind turbines in the offshore wind farm is determined by the following method:

[0013] Calculate the reactive power output at the grid - connection point of the offshore wind farm in the preset normal operation voltage range of the point of common coupling, the active power output level range of wind turbines, and the power factor range of wind turbines in sequence;

[0014] Set the reactive power output at the grid - connection point and the active power output of the wind turbines as control variables, and with the minimum reactive power deficit of the offshore wind farm as the objective function, calculate the maximum reactive power compensation demand of the offshore wind farm within the preset normal operation voltage range of the point of common coupling.

[0015] As a further improvement, the preset normal operation voltage range of the point of common coupling includes 0.97 p.u. to 1.07 p.u.; the preset active power output level range of wind turbines is 0% to 100%; the preset power factor range of wind turbines is leading 0.95 or lagging 0.95.

[0016] As a further improvement, the objective function of the lower - layer operation model includes bus voltage deviation, active power loss of the wind farm, and dynamic reactive power margin, and the constraint conditions include power flow balance constraints and steady - state operation constraints.

[0017] Second aspect, the present invention further provides a reactive power configuration device for an offshore wind farm, including:

[0018] A model construction module for constructing a two-layer programming model for reactive power configuration of an offshore wind farm, the model including an upper-layer configuration model and a lower-layer operation model;

[0019] A first calculation module for making the upper-layer configuration model aim at minimizing the annual investment cost of reactive power compensation devices, and using dynamic voltage security constraints and the minimum compensation capacity constraints of the offshore wind farm as constraint conditions to determine the initial reactive power configuration capacity, and transferring the initial reactive power configuration capacity to the lower-layer operation model;

[0020] A second calculation module for making the lower-layer operation model calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and returning the minimum annual operation cost of the offshore wind farm to the upper-layer configuration model;

[0021] A third calculation module for making the upper-layer configuration model calculate the optimal reactive power configuration capacity of the offshore wind farm according to the minimum annual investment cost of reactive power compensation devices and the received minimum annual operation cost of the offshore wind farm.

[0022] As a further improvement, the dynamic voltage security constraints are determined according to the voltage adaptability requirements, steady-state voltage requirements, and low-voltage ride-through operation requirements under the grid connection standard of the offshore wind farm; the minimum compensation capacity constraints of the offshore wind farm are determined according to the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of wind turbines.

[0023] As a further improvement, the objective function of the lower-layer operation model includes bus voltage deviation, active power loss of the wind farm, and dynamic reactive power margin, and the constraint conditions include power flow balance constraints and steady-state operation constraints.

[0024] Third aspect, the present invention provides a data processing device, including a processor, the processor is coupled with a memory, the memory stores a program, the program is executed by the processor, so that the data processing device executes the reactive power configuration method for an offshore wind farm described in the first aspect.

[0025] Fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, when the computer program is executed by a processor, it realizes the reactive power configuration method for an offshore wind farm as described in the above first aspect.

[0026] Compared with the prior art, the reactive power configuration method for an offshore wind farm provided by the present invention has at least the following beneficial effects:

[0027] The present invention takes into account the planning requirements in two stages of the configuration and operation of an offshore wind farm, makes full use of the reactive power regulation ability of wind turbines to reduce the reactive power compensation capacity, and at the same time adopts a dynamic optimization method to ensure the dynamic voltage security of the offshore wind farm under the obtained optimal reactive power configuration, and improves the economic efficiency of the offshore wind farm by minimizing the annual comprehensive cost. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 is a schematic flowchart of the reactive power configuration method for an offshore wind farm provided by an embodiment of the present invention;

[0030] Figure 2 is a schematic flowchart for solving the double-layer planning model of reactive power configuration for an offshore wind farm provided by an embodiment of the present invention;

[0031] Figure 3 is a schematic diagram of the structure of an offshore wind farm provided by an embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of the reactive power output of an offshore wind farm provided by an embodiment of the present invention;

[0033] Figure 5 is a schematic diagram of the steady-state reactive power demand of an offshore wind farm provided by an embodiment of the present invention;

[0034] Figure 6 is a schematic diagram of the simulation results during the low-voltage ride-through of an offshore wind farm provided by an embodiment of the present invention;

[0035] Figure 7 is a schematic diagram of the simulation results during the voltage adaptability test of an offshore wind farm provided by an embodiment of the present invention;

[0036] Figure 8 is a schematic diagram of the reactive power optimization results of an offshore wind farm provided by an embodiment of the present invention. Detailed Embodiments

[0037] This part will describe the specific embodiments of the present invention in detail. The preferred embodiments of the present invention are shown in the drawings. The role of the drawings is to supplement the description in the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be construed as a limitation on the protection scope of the present invention.

[0038] In a first aspect, to address the deficiencies in the current research on reactive power allocation in offshore wind farms, an embodiment of the present invention provides a method for reactive power allocation in an offshore wind farm, as follows: Figure 1 As shown, the method includes the following steps.

[0039] S1: Construct a two - layer programming model for reactive power allocation in an offshore wind farm, where the model includes an upper - layer allocation model and a lower - layer operation model.

[0040] S2: The upper - layer allocation model aims to minimize the annual investment cost of reactive power compensation devices, and takes the dynamic voltage security constraint and the minimum compensation capacity constraint of the offshore wind farm as constraints to determine the initial reactive power allocation capacity, and transfers the initial reactive power allocation capacity to the lower - layer operation model.

[0041] Specifically, the dynamic voltage security constraint is determined according to the voltage adaptability requirements, steady - state voltage requirements, and low - voltage ride - through operation requirements under the grid - connection standard of the offshore wind farm; the minimum compensation capacity constraint of the offshore wind farm is determined according to the maximum reactive power compensation demand after considering the reactive power regulation ability of wind turbines.

[0042] In this embodiment, by establishing a dynamic voltage security constraint in the upper - layer allocation model, the transient and dynamic voltage security of the offshore wind farm can be ensured under the optimal reactive power allocation and the reactive power support of wind turbines.

[0043] S3: The lower - layer operation model calculates the minimum annual operation cost of the offshore wind farm based on the initial reactive power allocation capacity and returns the minimum annual operation cost of the offshore wind farm to the upper - layer allocation model.

[0044] Specifically, the objective function of the lower - layer operation model includes bus voltage deviation, active power loss of the wind farm, and dynamic reactive power margin, and the constraint conditions include power flow balance constraint and steady - state operation constraint.

[0045] In this embodiment, the lower - layer operation model set coordinates the output of reactive power sources by considering the active power loss of the wind farm, dynamic reactive power margin, and bus voltage deviation index, and can make full use of the reactive power regulation ability of wind turbines to reduce the compensation capacity and operation cost.

[0046] S4: The upper - layer allocation model calculates the optimal reactive power allocation capacity of the offshore wind farm according to the minimum annual investment cost of reactive power compensation devices and the received minimum annual operation cost of the offshore wind farm.

[0047] It can be understood that the annual comprehensive cost of the offshore wind farm includes the annual investment cost of reactive power compensation devices and the annual operation cost of the offshore wind farm. By minimizing the annual comprehensive cost in the model solution process, the economic benefits of the offshore wind farm can be effectively improved.

[0048] In one example, the maximum reactive power compensation requirement of an offshore wind farm considering the reactive power regulation ability of wind turbines can be determined in the following manner:

[0049] Calculate the reactive power output at the grid connection point of the offshore wind farm in sequence under the preset normal operating voltage range of the point of common coupling, the preset active power output level range of the wind turbines, and the preset power factor range of the wind turbines. Set the reactive power output at the grid connection point and the active power output of the wind turbines as control variables, and set the minimization of the reactive power deficit of the offshore wind farm as the objective function, and calculate and determine the maximum reactive power compensation requirement of the offshore wind farm within the preset normal operating voltage range of the point of common coupling.

[0050] Specifically, the preset normal operating voltage range of the point of common coupling includes 0.97 p.u. to 1.07 p.u.; the preset active power output level range of the wind turbines is 0% to 100%; the preset power factor range of the wind turbines is leading 0.95 or lagging 0.95.

[0051] The following will introduce the implementation process of the reactive power configuration method for an offshore wind farm through a specific example.

[0052] In this example, first establish a two-layer programming model for reactive power configuration of the offshore wind farm, where the model includes an upper-layer configuration model and a lower-layer operation model.

[0053] Specifically, the objective function of the upper-layer configuration model is the annual comprehensive cost composed of the annual investment cost of the reactive power compensation device and the annual operation cost of the offshore wind farm, which can be expressed as:

[0054] minF1 = C inv + C op

[0055] C inv = A(i s , n s )C stat Q stat + A(i h , n h )C hvsr Q hvsr

[0056]

[0057] In the formula, C inv represents the annual investment cost of the reactive power compensation device; C op represents the annual operation cost of the offshore wind farm; A(i, n) represents the investment recovery factor; C stat C hvsr respectively represent the unit capacity investment costs of the static synchronous compensator (STATCOM) and the high-voltage shunt reactor (HVSR); Q statand Q hvsr represent the compensation capacities of the static synchronous compensator (STATCOM) and the high - voltage shunt reactor (HVSR) respectively; i represents the discount rate of the reactive power compensation device; n represents the service life.

[0058] The constraint conditions of the upper - layer configuration model include dynamic voltage security constraints and minimum compensation capacity constraints. Among them, the dynamic voltage security constraints are established according to the requirements of the grid - connection standard of the offshore wind farm for voltage adaptability, steady - state voltage, voltage during low - voltage ride - through, and the active power recovery speed of dynamic reactive power support; the minimum compensation capacity constraint is determined according to the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of the wind turbines.

[0059] Specifically, the constraint conditions of the upper - layer configuration model can be expressed as:

[0060]

[0061]

[0062]

[0063] 0.97U N ≤U poc (t)≤1.07U N ,t≥t ss

[0064]

[0065] Q stat +U poc,max 2 Q hvsr ≥Q com.min

[0066] In the formula, B represents the set of wind turbine buses, U i represents the voltage of the i - th wind turbine bus, T1 represents the low - voltage ride - through time; LVRT(t) represents the required curve of the node voltage during low - voltage ride - through in the grid - connection standard of the offshore wind farm; I q represents the dynamic reactive current injected into the grid by the offshore wind farm, I N represents the rated current of the grid - connection point; and represent the active power when the wind farm returns to the steady state and when the fault is eliminated respectively. represents the rated active power of the offshore wind farm; U N represents the rated voltage of the grid - connection point, T2 represents the voltage adaptability detection time period, U poc represents the voltage of the grid - connection point; Q com.min represents the minimum compensation capacity.

[0067] It should be noted that among the constraint conditions set by the upper-layer configuration model, the minimum compensation capacity constraint needs to be determined through the following method:

[0068] First, analyze the reactive power characteristics of the offshore wind farm and the reactive power regulation ability of the permanent magnet synchronous wind turbine, and calculate the reactive power deficit of the offshore wind farm considering the reactive power regulation ability of the wind turbine units.

[0069] Specifically, establish a reactive power-voltage calculation model based on the reactive power characteristics of each device in the offshore wind farm, and gradually calculate the reactive power output of the offshore wind farm when the active power output level Pout% of the wind turbine units is in the range of 0% to 100%, the power factor PF of the wind turbine units is leading 0.95 or lagging 0.95, and the normal operating voltage U of the point of common coupling pcc is in the range of 0.97 p.u. to 1.07 p.u., that is, the reactive power Q at the point of connection poc , and analyze the influence of each variable on the reactive power output.

[0070] Furthermore, establish an optimal power flow model based on the above reactive power-voltage calculation model. The optimal power flow model takes the active power output and reactive power output of the wind turbine units as control variables, aims to minimize the reactive power deficit of the offshore wind farm, gradually increases the voltage value within the normal operating voltage range of the point of common coupling, and calculates the possible reactive power deficit of the offshore wind farm under normal operating conditions, that is, the maximum reactive power compensation demand. This maximum reactive power compensation demand is the minimum compensation capacity of the offshore wind farm considering the reactive power regulation ability of the wind turbine units.

[0071] Specifically, the objective function of the optimal power flow model is expressed as:

[0072]

[0073] In the formula, P out represents the active power output of the wind turbine units, U pcc represents the normal operating voltage of the point of common coupling, and the voltage range is [0.97 p.u., 1.07 p.u.], Q out represents the reactive power output of the wind turbine units, represents the reactive power compensation amount at the point of connection, Q poc represents the reactive power at the point of connection.

[0074] When the normal operating voltage U of the point of common coupling pcc is close to the upper limit of 1.07 p.u., the point of connection will absorb reactive power from the grid side to avoid voltage exceeding the upper limit; therefore, in this embodiment, by adding a penalty term λQ poc to the objective function, the reactive power exchange between the offshore wind farm and the connected grid is reduced when the voltage is close to the upper limit of the normal operating range.

[0075] The constraint conditions of the optimal power flow model include:

[0076]

[0077] 0 ≤ P out ≤ P wtg.N

[0078] 0.97U poc.N ≤ U poc ≤ 1.07U poc.N

[0079] 0.90U wtg.N ≤ U wtg ≤ 1.10U wtg.N

[0080] Wherein, S con represents the rated capacity of the wind turbine converter, P wtg.N represents the rated power of the wind turbine, U poc and U wtg represent the grid connection point voltage and the wind turbine voltage respectively; U poc.N and U wtg.N represent the rated grid connection point voltage and the rated wind turbine voltage respectively.

[0081] Specifically, in the optimal power flow model, the step size can be set to 0.01 p.u., and the normal operating voltage U of the point of common coupling is gradually increased pcc , calculate the maximum reactive power compensation demand at each voltage level and the active power output level of the wind turbine, and use it as the minimum compensation capacity constraint of the upper-layer configuration model:

[0082] U pcc = 0.97 p.u. + 0.01n, n = 0, 1, …, 10

[0083]

[0084] In the above example, the upper-layer configuration model establishes a dynamic voltage security constraint with the minimum annual comprehensive cost as the objective function, which can ensure the transient and dynamic voltage security of the offshore wind farm under optimal reactive power configuration and the reactive power support of the wind turbine.

[0085] Specifically, when solving the upper-layer configuration model, the capacity of the reactive power compensation configuration device can be set as the control variable, with the minimum annual comprehensive cost as the objective, to obtain the initial reactive power configuration capacity, and the obtained initial reactive power configuration capacity is transmitted to the lower-layer operation model. Among them, the reactive power compensation configuration device includes a high-voltage shunt reactor (HVSR) and a static synchronous compensator (STATCOM).

[0086] In the process of solving the upper-layer configuration model, the responses of the offshore wind farm under various reactive power configurations can be obtained through dynamic simulation, and then it can be verified whether the corresponding reactive power configuration meets the constraint conditions of the model.

[0087] On the other hand, the objective function of the lower-layer operation model is the bus voltage deviation, the active power loss of the wind farm, and the dynamic reactive power margin, which can be expressed as:

[0088] minF2 = λ1f Q,mar +λ2f V +λ3f Ploss

[0089]

[0090]

[0091]

[0092] In the formula, f Q,mar represents the dynamic reactive power margin index, f V represents the bus voltage deviation index, f Ploss represents the active power loss index, λ1, λ2, and λ3 respectively represent the weight coefficients of each index in the objective function; μ c and μ i respectively represent the capacitive and inductive reactive power margin coefficients, and μ c < μ i , and respectively represent the sets of dynamic reactive power source nodes that emit capacitive reactive power and inductive reactive power, Q j represents the reactive power injected by node j, Q j,cmax and Q j,imax respectively represent the adjustable capacitive reactive power upper limit and the adjustable inductive reactive power upper limit of the dynamic reactive power source j, Q c.thr and Q i.thr respectively represent the capacitive and inductive reactive power thresholds of the dynamic reactive power source. When the reactive power output exceeds the threshold, it is restricted by the reactive power margin index. If it does not exceed the threshold, the reactive power output is not restricted; U i represents the voltage of node i, U i.ref represents the reference voltage of node i; I ij represents the current flowing from node i to node j, r ij represents the resistance of the ij branch, and W represents the set of nodes in the wind farm.

[0093] It is understandable that in order to ensure that the offshore wind farm can provide sufficient dynamic reactive power to support voltage stability in the event of faults and wind power fluctuations, during steady-state operation, each dynamic reactive power source should reserve a certain amount of reactive power capacity. At the same time, different reactive power distribution coefficients are set for each reactive power source according to the reactive power-voltage sensitivity, and different margins are set for capacitive and inductive reactive power.

[0094] The constraint conditions of the lower-layer operation model include power flow constraints and steady-state operation constraints. Among them, the steady-state operation constraints include the upper and lower limits of node voltage, the upper and lower limits of adjustable reactive power of reactive power sources, and the upper and lower limits of adjustable tap positions of transformers, which can be expressed as:

[0095] U i,min ≤U i ≤U i,max

[0096] Q i,min ≤Q i ≤Q i,max

[0097] T i,min ≤T i ≤T i,max

[0098] In the formula, U i,min and U i,max respectively represent the upper and lower limits of the voltage of node i; Q i,min and Q i,max respectively represent the upper and lower limits of the adjustable reactive power of the dynamic reactive power source i; T i,min and T i,max respectively represent the upper and lower limits of the adjustable tap positions of transformer i.

[0099] The lower-layer operation model coordinates the distribution of reactive power source output by considering network loss, reactive power margin, and voltage deviation index, and can make full use of the reactive power regulation ability of wind turbines to reduce reactive power compensation capacity and annual operating cost.

[0100] In the process of model solution, the lower-layer planning model takes the output of dynamic reactive power sources and the tap positions of main transformers as control variables. After solving the optimization results according to the model objective function and constraint conditions, the average monthly active power output of the offshore wind farm is selected for reactive power optimization, and the annual active power loss is calculated according to the optimization results. Finally, the calculated annual active power loss is transmitted to the upper-layer configuration model as the annual operating cost.

[0101] Specifically, the calculation method of the annual operating cost is:

[0102]

[0103] In the formula, C loss represents the active power loss cost per degree of electricity, h(i) represents the number of hours in the i-th month, and Ploss (i) represents the active power loss of the wind farm under the average active power output in the i-th month.

[0104] Furthermore, the upper-layer configuration model adds the annual operating cost optimized by the lower-layer operation model to the objective function, and makes full use of the reactive power regulation ability of wind turbines to avoid the increase in active power network loss caused by low reactive power configuration capacity and large reactive power output of wind turbines, thereby solving for the optimal reactive power configuration capacity of the offshore wind farm.

[0105] In one embodiment, the bi-level programming model for reactive power configuration of the offshore wind farm can be solved by a genetic algorithm.

[0106] Specifically, the upper-layer configuration model belongs to integer programming and can be solved by a genetic algorithm, and time-domain simulation is carried out using Matlab / Simulink to verify the dynamic voltage security constraints; the lower-layer operation model belongs to mixed integer programming and can be transformed into second-order cone programming and then solved using the CPLEX algorithm package.

[0107] Please refer to Figure 2 , the specific solution process of the bi-level programming model for reactive power configuration of the offshore wind farm is as follows:

[0108] 1) Input the parameters of the offshore wind farm (active power output level of wind turbines, power factor of wind turbines, and normal operating voltage of the point of common coupling), establish an optimal power flow model for reactive power voltage calculation of the offshore wind farm, and calculate the minimum compensation capacity of the offshore wind farm;

[0109] 2) Set the algorithm parameters, perform genetic coding on the variables of the upper-layer configuration model, and generate an initial population, where the initial population includes two control variables, namely the STATCOM and HVSR capacities.

[0110] 3) Input the individuals in the initial population into the time-domain simulation model to verify whether the reactive power compensation configuration within the current initial population can meet the constraint requirements for dynamic voltage, dynamic reactive power support, active power recovery, voltage adaptability, and steady-state voltage recovery. If the requirements are not met, the time-domain simulation terminates and a new generation of population is generated.

[0111] 4) Transfer the initial population obtained from the upper-layer configuration model to the lower-layer operation model, solve the lower-layer operation model to calculate the optimized annual operating cost of the wind farm, and return it to the upper-layer configuration model.

[0112] 5) Calculate the annual investment cost according to the upper-layer population that passes the time-domain simulation; at the same time, calculate the objective function value (annual comprehensive cost) of the upper-layer configuration model by combining the annual operating cost returned by the lower-layer operation model, and update the best individual.

[0113] 6) Determine whether the optimization termination condition is reached. If the termination condition is met, the optimization terminates and the final optimization result is output. If the termination condition is not met, select, crossover, and mutate the current population to generate the next generation population.

[0114] It should be noted that the above-mentioned optimization termination condition means that under the condition of the minimum compensation capacity generated by the algorithm, the offshore wind farm system satisfies static, dynamic, and transient voltage stability, and there is no resonance in the system, that is, it meets the upper-layer configuration model constraint conditions.

[0115] The finally obtained optimization result includes the optimal STATCOM capacity and the optimal HVSR capacity.

[0116] In the above embodiments of the present invention, by considering the planning requirements of the configuration and operation stages of the offshore wind farm, and coordinating the output of dynamic reactive power sources in combination with the network loss, reactive power margin, and voltage deviation indicators, the reactive power regulation ability of the wind turbines is fully utilized to reduce the reactive power compensation capacity, and the economic benefits of the offshore wind farm are improved by taking the minimum annual comprehensive cost as the goal.

[0117] Furthermore, in the above embodiments of the present invention, specifically through the dynamic optimization method, the dynamic voltage safety of the offshore wind farm under the optimal reactive power compensation configuration is guaranteed. Compared with the traditional static optimization method, in the optimization process of the present invention, the time-domain simulation is used to directly verify whether the configuration scheme meets the requirements of the dynamic and transient process indicators of the offshore wind farm grid connection standard, which can more effectively ensure the safety of dynamic voltage and transient state.

[0118] In order to better reflect the actual technical effects of the technical solution of the present invention, the following will describe its implementation and application process through another specific embodiment:

[0119] In this embodiment, the offshore wind farm contains 55 5.5MW permanent magnet direct drive wind turbines, and its structure diagram is as Figure 3 shown.

[0120] Specifically, the collector system adopts a chain structure, and two double-split transformers are set in the offshore booster station, and power is transmitted to the onshore centralized control center through 44.6 km double-circuit submarine cables, and then input into the power grid through 13.7 km overhead lines. The relevant parameters of the test system are shown in Table 1 below.

[0121] Table 1

[0122]

[0123]

[0124] Furthermore, by constructing a reactive power-voltage calculation model, the reactive power characteristics of the offshore wind farm are analyzed.

[0125] Specifically,Figure 4 It provides the reactive power output of an offshore wind farm within the range of 0% to 100% of the active power output level Pout% of a wind turbine generator set, with the power factor PF of the wind turbine generator set being 0.95 leading or 0.95 lagging, and the normal operating voltage U of the point of common coupling pcc within the range of 0.97 p.u. to 1.07 p.u.

[0126] Combined with Figure 4 it can be seen that the higher the voltage at the point of connection, the greater the charging power of the submarine cable; the less the active power output of the wind turbine generator set, the smaller the reactive power loss. Therefore, when the voltage at the point of connection increases and the active power output of the wind turbine generator set decreases, the reactive power deficit of the offshore wind farm will increase, which also shows that the model calculation results are consistent with the reactive power characteristics of the equipment, proving that the reactive power of the long-distance submarine cable is the key affecting the reactive power characteristics of the offshore wind farm. Therefore, in the process of reactive power compensation configuration, the influence of the voltage at the point of connection and the active power output of the wind turbine generator set on the reactive power of the offshore wind farm should be fully considered.

[0127] Furthermore, based on the reactive power-voltage calculation model, the minimum compensation capacity of the offshore wind farm is calculated.

[0128] Specifically, an optimal power flow model is established according to the above reactive power-voltage calculation model, and within the range of [0.97 p.u., 1.07 p.u.], with a step of 0.01 p.u., the normal operating voltage of the point of common coupling is gradually increased, and the maximum reactive power compensation demand that may occur under steady state is calculated.

[0129] Figure 5 It provides the reactive power demand of the offshore wind farm under different steady-state conditions. Combined with Figure 5 it can be seen that when the active power output level of the wind turbine generator set is 31.1% and the voltage at the point of connection is 1.07 p.u., the maximum reactive power demand, that is, the minimum compensation capacity Q com.min is 97.94 Mvar.

[0130] Furthermore, the pre-constructed bi-level programming model for reactive power configuration of the offshore wind farm is calculated to obtain the optimal reactive power configuration capacity.

[0131] Specifically, in the time-domain simulation of the upper-layer configuration model, low-voltage ride-through tests and voltage adaptability tests are set up to verify whether the reactive power compensation configuration scheme meets the requirements of various indicators of the offshore wind farm grid connection standard.

[0132] Among them, the two dynamic voltage tests are set based on the grid connection standard as follows:

[0133] First, the grid voltage drops to 20% of the nominal voltage at 2.5 s and recovers to the rated voltage after 625 ms;

[0134] II. The grid connection point voltage drops to 90% of the nominal voltage from 5 s to 5.5 s, rises to 110% of the nominal voltage from 6 s to 6.5 s, and returns to the rated voltage at 6.5 s.

[0135] Under the optimal reactive power compensation configuration scheme, during two dynamic voltage events of the offshore wind farm, the simulation results of the grid connection point voltage, the dynamic reactive current support of the wind farm, the reactive power output of the STATCOM, the voltage of the wind turbine generator, the active power output and the reactive power output are as Figure 6 and Figure 7 shown.

[0136] As Figure 6 shown, when the grid voltage suddenly drops to 0.2 p.u., with the reactive power support of the STATCOM and the wind turbine generators, the grid connection point voltage and the extreme voltage of the wind turbine generators drop to 0.249 p.u. and 0.323 p.u. respectively, and quickly recover after the fault disappears, and can maintain non-disconnection from the grid. After the voltage drops, the STATCOM quickly changes from absorbing reactive power to outputting reactive power, and the reactive current output capacity is not affected by the voltage. Under the action of the STATCOM, the reactive current input into the grid by the wind farm during the fault increases by 0.233 p.u., which can meet the requirements of the grid connection standard for dynamic reactive current support. The active power output of the wind turbine generators drops to 19 MW, and the recovery speed after the fault is greater than 10% / s.

[0137] As Figure 7 shown, when the grid connection point voltage is at 0.9 p.u. and 1.1 p.u., the STATCOM outputs the maximum reactive current to restore the voltage to the steady-state value. The active power of the wind turbine generators decreases slightly, and the terminal voltage of the generators is within the normal operating voltage range. Since both the STATCOM and the wind turbine generators absorb reactive power during steady-state operation and the capacitive reactive power margin is small, when the grid connection point voltage rises, the terminal voltage of the wind turbine generators is closer to the voltage upper limit, but still does not exceed the limit.

[0138] From the above time-domain simulation results, it can be seen that the obtained optimal reactive power compensation configuration scheme can ensure the dynamic voltage safety of the offshore wind farm and meet the requirements of the grid connection standard.

[0139] Specifically, Table 2 and Table 3 below provide the detailed parameters of the optimization model such as the compensation cost per unit capacity, the discount rate, etc., as well as the comparison between the optimization results of the obtained optimal reactive power compensation configuration scheme and the current actual configuration scheme:

[0140] Table 2

[0141] parameter numerical value Cstat, Chvsr 300,000 yuan / Mvar, 50,000 yuan / Mvar is, ih 5％ nstat, nhvsr 20 years, 25 years Closs 694.8 yuan / MWh Qc.thr, Qi.thr 0.65Qc.max, 0.5Qi.max

[0142] Table 3

[0143] —— actual scheme optimized scheme Qstat (Mvar) 72 47 Qhvsr (Mvar) 118 94 Cinv (10,000 yuan) 223.56 153.18 Cop (10,000 yuan) 884.76 885.18 annual comprehensive cost (10,000 yuan) 1108.32 1038.36

[0144] As can be seen from Table 2 and Table 3 above, in the optimal reactive power allocation scheme obtained by the above technical method of the present invention, the capacities of both the STATCOM and the high-voltage shunt reactor are less than those of the actual scheme. The annual operating cost has increased by only 0.42×10,000 yuan, but the annual investment cost has decreased by 70.38×10,000 yuan, a reduction of 31.5%; the annual comprehensive cost has decreased by 69.96×10,000 yuan, a reduction of 6.31%.

[0145] Furthermore, Figure 8 The reactive power optimization results of each reactive power source under the average active power output of each month are provided.

[0146] It can be understood that, compared with the actual capacity, the optimal reactive power allocation capacity obtained in the embodiment of the present invention is smaller. Therefore, when operating, more reactive power needs to be generated by the wind turbines for compensation. When the reactive power flows in the system, the network loss increases, resulting in a slight increase in the annual operating cost.

[0147] Specifically, the HVSR capacity determined in the embodiment of the present invention is small. Therefore, the STATCOM needs to output more reactive power. When its value exceeds the threshold of the dynamic reactive power margin index in the lower-layer operation model, the output of the STATCOM will be limited, and the required reactive power will be borne by the wind turbines. Combining Figure 8 It can be seen that from February to October, the wind turbines in the embodiment of the present invention generate more reactive power, the STATCOM is restricted, and the reactive power output is less than that in January, November, and December.

[0148] Although the above embodiments of the present invention improve the reactive power output of the dynamic reactive power source and make full use of the reactive power regulation capabilities of the STATCOM and the wind turbines, they also reserve sufficient dynamic reactive power margins, slightly increase the annual operating cost, and greatly reduce the annual investment cost and the annual comprehensive cost, generally improving the economic benefits of the offshore wind farm.

[0149] In a second aspect, another embodiment of the present invention further provides an offshore wind farm reactive power allocation device, including a model construction module, a first calculation module, a second calculation module, and a third calculation module.

[0150] Among them, the model construction module is used to construct a two-layer programming model for the reactive power allocation of the offshore wind farm, and the model includes an upper-layer configuration model and a lower-layer operation model.

[0151] The first calculation module is used to make the upper-layer configuration model aim at minimizing the annual investment cost of the reactive power compensation device, and use the dynamic voltage security constraint and the minimum compensation capacity constraint of the offshore wind farm as the constraint conditions to determine the initial reactive power allocation capacity, and transfer the initial reactive power allocation capacity to the lower-layer operation model.

[0152] The second calculation module is used to make the lower-layer operation model calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and return the minimum annual operation cost of the offshore wind farm to the upper-layer configuration model.

[0153] The third calculation module is used to make the upper-layer configuration model calculate the optimal reactive power configuration capacity of the offshore wind farm according to the minimum annual investment cost of the reactive power compensation device and the received minimum annual operation cost of the offshore wind farm.

[0154] Regarding the information interaction, execution process, etc. among the modules in the above device, since they are based on the same concept as the method embodiment of the present invention, the specific content can be referred to the description in the method embodiment of the present invention, and will not be elaborated here.

[0155] In a third aspect, the present invention provides a data processing device, including a processor, the processor is coupled with a memory, the memory stores a program, and the program is executed by the processor, so that the data processing device executes the offshore wind farm reactive power configuration method described in the first aspect.

[0156] In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the offshore wind farm reactive power configuration method described in the first aspect above.

[0157] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0158] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

Claims

1. A reactive power configuration method for an offshore wind farm, characterized in that Including: Construct a two - layer planning model for reactive power configuration of an offshore wind farm, where the model includes an upper - layer configuration model and a lower - layer operation model; Let the upper - layer configuration model aim at minimizing the annual investment cost of reactive power compensation devices, with dynamic voltage security constraints and the minimum compensation capacity constraint of the offshore wind farm as constraints, determine the initial reactive power configuration capacity, and transfer the initial reactive power configuration capacity to the lower - layer operation model; among them, the minimum compensation capacity constraint of the offshore wind farm is determined according to the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of wind turbines; the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of wind turbines is determined by the following method: successively calculate the reactive power output power at the connection point of the offshore wind farm under the normal operating voltage range of the preset point of common coupling, the active power output level range of wind turbines, and the power factor range of wind turbines; set the reactive power output power at the connection point and the active power output of the wind turbines as control variables, and the minimum reactive power deficit of the offshore wind farm as the objective function, and calculate the maximum reactive power compensation demand of the offshore wind farm within the preset normal operating voltage range of the point of common coupling; Let the lower - layer operation model calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and return the minimum annual operation cost of the offshore wind farm to the upper - layer configuration model; Let the upper - layer configuration model calculate the optimal reactive power configuration capacity of the offshore wind farm according to the minimum annual investment cost of reactive power compensation devices and the received minimum annual operation cost of the offshore wind farm.

2. The reactive power configuration method for an offshore wind farm according to claim 1, wherein In the upper - layer configuration model, The dynamic voltage security constraint is determined according to the voltage adaptability requirements, steady - state voltage requirements, and low - voltage ride - through operation requirements under the grid - connection standard of the offshore wind farm.

3. The method for reactive power configuration of an offshore wind farm according to claim 2, characterized in that, The preset normal operating voltage range of the point of common coupling includes 0.97 p.u. to 1.07 p.u.; The preset active power output level range of wind turbines is 0% to 100%; The preset power factor range of wind turbines is leading 0.95 or lagging 0.

95.

4. The method for reactive power configuration of an offshore wind farm according to claim 1, characterized in that, The objective function of the lower - layer operation model includes bus voltage deviation, active power loss of the wind farm, and dynamic reactive power margin, and the constraint conditions include power flow balance constraint and steady - state operation constraint.

5. A reactive power configuration device for an offshore wind farm, characterized in that, Including: A model construction module for constructing a two - layer planning model for reactive power configuration of an offshore wind farm, where the model includes an upper - layer configuration model and a lower - layer operation model; A first calculation module, configured to enable the upper-layer configuration model to determine an initial reactive power configuration capacity with the goal of minimizing the annual investment cost of the reactive power compensation device and with the dynamic voltage security constraint and the minimum compensation capacity constraint of the offshore wind farm as the constraint conditions, and transmit the initial reactive power configuration capacity to the lower-layer operation model; wherein, the minimum compensation capacity constraint of the offshore wind farm is determined according to the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of the wind turbines; the maximum reactive power compensation demand of the offshore wind farm considering the reactive power regulation ability of the wind turbines is determined by the following method: sequentially calculate the reactive power output power of the connection point of the offshore wind farm under the normal operating voltage range of the preset point of common coupling, the active power output level range of the wind turbines, and the power factor range of the wind turbines; set the reactive power output power of the connection point and the active power output of the wind turbines as control variables, and with the minimization of the reactive power deficit of the offshore wind farm as the objective function, calculate the maximum reactive power compensation demand of the offshore wind farm within the normal operating voltage range of the preset point of common coupling. A second calculation module, configured to enable the lower-layer operation model to calculate the minimum annual operation cost of the offshore wind farm based on the initial reactive power configuration capacity, and return the minimum annual operation cost of the offshore wind farm to the upper-layer configuration model. A third calculation module, configured to enable the upper-layer configuration model to calculate the optimal reactive power configuration capacity of the offshore wind farm according to the minimum annual investment cost of the reactive power compensation device and the received minimum annual operation cost of the offshore wind farm.

6. The reactive power configuration device for an offshore wind farm according to claim 5, wherein the dynamic voltage security constraint is determined according to the voltage adaptability requirements, steady-state voltage requirements, and low voltage ride-through operation requirements under the grid connection standard of the offshore wind farm.

7. The reactive power configuration device for an offshore wind farm according to claim 6, wherein the objective function of the lower-layer operation model includes bus voltage deviation, active power loss of the wind farm, and dynamic reactive power margin, and the constraint conditions include power flow balance constraint and steady-state operation constraint.

8. A data processing device, characterized in that, including: a processor, the processor is coupled with a memory, the memory stores a program, and the program is executed by the processor, so that the data processing device executes the reactive power configuration method for an offshore wind farm according to any one of claims 1 to 4.

9. A computer storage medium, characterized in that, The computer storage medium stores computer instructions, and the computer instructions are used to execute the reactive power configuration method for an offshore wind farm according to any one of claims 1 to 4 above.

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